Update kubeconfig-file doc.

docs/kubeconfig-file.md

-# .kubeconfig files
-In order to easily switch between multiple clusters, a .kubeconfig file was defined.  This file contains a series of authentication mechanisms and cluster connection information associated with nicknames.  It also introduces the concept of a tuple of authentication information (user) and cluster connection information called a context that is also associated with a nickname.
+# kubeconfig files
+In order to easily switch between multiple clusters, a kubeconfig file was defined.  This file contains a series of authentication mechanisms and cluster connection information associated with nicknames.  It also introduces the concept of a tuple of authentication information (user) and cluster connection information called a context that is also associated with a nickname.
 
-Multiple files are .kubeconfig files are allowed.  At runtime they are loaded and merged together along with override options specified from the command line (see rules below).
+Multiple files are kubeconfig files are allowed.  At runtime they are loaded and merged together along with override options specified from the command line (see rules below).
 
 ## Related discussion
 https://github.com/GoogleCloudPlatform/kubernetes/issues/1755
 
-## Example .kubeconfig file
+## Example kubeconfig file
 ```
 apiVersion: v1
 clusters:
@@ -38,9 +38,6 @@ kind: Config
 preferences:
   colors: true
 users:
-- name: black-user
-  user:
-    auth-path: path/to/my/existing/.kubernetes_auth_file
 - name: blue-user
   user:
     token: blue-token
@@ -54,9 +51,9 @@ users:
 
 ## .kubernetes_auth files
 
-**WARNING**: merging auth from a mixture of kubernetes_auth file entries and .kubeconfig user entries is hard to debug and should be avoided. kubernetes_auth file support exists mostly for tests and is being deprecated.
+**WARNING**: merging auth from a mixture of kubernetes_auth file entries and kubeconfig user entries is hard to debug and should be avoided. kubernetes_auth file support exists mostly for tests and is being deprecated.
 
-The kubernetes_auth file is a legacy config file that can contain a mix of server and client auth info. It is supported in .kubeconfig via `auth-path` for a user:
+The kubernetes_auth file is a legacy config file that can contain a mix of server and client auth info. It is supported in kubeconfig via `auth-path` for a user:
 ```
 users:
 - name: black-user
@@ -80,10 +77,10 @@ The entries in a file loaded via auth-path will be applied to both the user and
 ```
 All entries are optional. `User`, `Password`, `CertFile`, `KeyFile`, and `BearerToken` are applied to the kubectl user. `CAFile` and `Insecure` apply to the cluster. Note that it is invalid to set both `CAFile` and `Insecure`, or both `BearerToken` and `User,Password` (see loading and merging rules below).
 
-If the contents of the kubernetes_auth file conflict with entries in .kubeconfig, they are ignored. E.g, if the .kubeconfig cluster specifies a `certificate-authority`, and the user specifies an `auth-path` to a kubernetes_file that contains a `CAFile` entry, the former will be used and the latter ignored.
+If the contents of the kubernetes_auth file conflict with entries in kubeconfig, they are ignored. E.g, if the kubeconfig cluster specifies a `certificate-authority`, and the user specifies an `auth-path` to a kubernetes_file that contains a `CAFile` entry, the former will be used and the latter ignored.
 
 ## Loading and merging rules
-The rules for loading and merging the .kubeconfig files are straightforward, but there are a lot of them.  The final config is built in this order:
+The rules for loading and merging the kubeconfig files are straightforward, but there are a lot of them.  The final config is built in this order:
   1.  Get the kubeconfig  from disk.  This is done with the following hierarchy and merge rules:
 
 
@@ -111,35 +108,18 @@ The rules for loading and merging the .kubeconfig files are straightforward, but
       1.  If cluster info is present and a value for the attribute is present, use it.
       1.  If you don't have a server location, error.
   1.  Determine the actual user info to use. User is built using the same rules as cluster info, EXCEPT that you can only have one authentication technique per user.
-      1. Load precedence is 1) command line flag, 2) user fields from .kubeconfig, 3) kubernetes_auth file fields (if user has a `auth-path` or the `--auth-path` was provided)
+      1. Load precedence is 1) command line flag, 2) user fields from kubeconfig, 3) kubernetes_auth file fields (if user has a `auth-path` or the `--auth-path` was provided)
       1. The command line flags are: `auth-path`, `client-certificate`, `client-key`, `username`, `password`, and `token`.
       1. If there are two conflicting techniques, fail.
   1.  For any information still missing, use default values and potentially prompt for authentication information
 
-## Manipulation of .kubeconfig via `kubectl config <subcommand>`
-In order to more easily manipulate .kubeconfig files, there are a series of subcommands to `kubectl config` to help.
-```
-kubectl config set-credentials name --auth-path=path/to/authfile --client-certificate=path/to/cert --client-key=path/to/key --token=string
-  Sets a user entry in .kubeconfig.  If the referenced name already exists, it will be overwritten.
-kubectl config set-cluster name --server=server --skip-tls=bool --certificate-authority=path/to/ca --api-version=string
-  Sets a cluster entry in .kubeconfig.  If the referenced name already exists, it will be overwritten.
-kubectl config set-context name --user=string --cluster=string --namespace=string
-  Sets a config entry in .kubeconfig.  If the referenced name already exists, it will be overwritten.
-kubectl config use-context name
-  Sets current-context to name
-kubectl config set property-name property-value
-  Sets arbitrary value in .kubeconfig
-kubectl config unset property-name
-  Unsets arbitrary value in .kubeconfig
-kubectl config view --local=true --global=false --kubeconfig=specific/filename --merged
-  Displays the merged (or not) result of the specified .kubeconfig file
-
---local, --global, and --kubeconfig are valid flags for all of these operations.
-```
+## Manipulation of kubeconfig via `kubectl config <subcommand>`
+In order to more easily manipulate kubeconfig files, there are a series of subcommands to `kubectl config` to help.
+See [docs/kubectl_config.md](kubectl_config.md) for help.
 
 ### Example
 ```
-$kubectl config set-credentials myself --auth-path=path/to/my/existing/auth-file
+$kubectl config set-credentials myself --username=admin --password=secret
 $kubectl config set-cluster local-server --server=http://localhost:8080
 $kubectl config set-context default-context --cluster=local-server --user=myself
 $kubectl config use-context default-context
@@ -160,10 +140,11 @@ current-context: default-context
 preferences: {}
 users:
   myself:
-    auth-path: path/to/my/existing/auth-file
+    username: admin
+    password: secret
 
 ```
-and a .kubeconfig file that looks like this
+and a kubeconfig file that looks like this
 ```
 apiVersion: v1
 clusters:
@@ -182,7 +163,8 @@ preferences: {}
 users:
 - name: myself
   user:
-    auth-path: path/to/my/existing/auth-file
+    username: admin
+    password: secret
 ```
 
 #### Commands for the example file
@@ -191,7 +173,6 @@ $kubectl config set preferences.colors true
 $kubectl config set-cluster cow-cluster --server=http://cow.org:8080 --api-version=v1beta1
 $kubectl config set-cluster horse-cluster --server=https://horse.org:4443 --certificate-authority=path/to/my/cafile
 $kubectl config set-cluster pig-cluster --server=https://pig.org:443 --insecure-skip-tls-verify=true
-$kubectl config set-credentials black-user --auth-path=path/to/my/existing/.kubernetes_auth_file
 $kubectl config set-credentials blue-user --token=blue-token
 $kubectl config set-credentials green-user --client-certificate=path/to/my/client/cert --client-key=path/to/my/client/key
 $kubectl config set-context queen-anne-context --cluster=pig-cluster --user=black-user --namespace=saw-ns