Automatic merge from submit-queue

Reorganize kubelet tree so apis can be independently versioned

@yujuhong @lavalamp @thockin @bgrant0607 
This is an example of how we might reorganize `pkg/kubelet` so the apis it exposes can be independently versioned. This would also provide a logical place to put the `KubeletConfiguration` type, which currently lives in `pkg/apis/componentconfig`; it could live in e.g. `pkg/kubelet/apis/config` instead.

Take a look when you have a chance and let me know what you think. The most significant change in this PR is reorganizing `pkg/kubelet/api` to `pkg/kubelet/apis`, the rest is pretty much updating import paths and `BUILD` files.