Addresses: kubernetes/features#88

This commit starts breaking the controller manager into two pieces, namely,

1. cloudprovider dependent piece
2. coudprovider agnostic piece

the controller manager has the following control loops -

   - nodeController
   - volumeController
   - routeController
   - serviceController
   - replicationController
   - endpointController
   - resourcequotacontroller
   - namespacecontroller
   - deploymentController etc..

among the above controller loops,

   - nodeController
   - volumeController
   - routeController
   - serviceController

are cloud provider dependent. As kubernetes has evolved tremendously, it has become difficult
for different cloudproviders (currently 8), to make changes and iterate quickly. Moreover, the
cloudproviders are constrained by the kubernetes build/release lifecycle. This commit is the first
step in moving towards a kubernetes code base where cloud providers specific code will move out of
the core repository, and will be maintained by the cloud providers themselves.

Finally, along with the controller-manager, the kubelet also has cloud-provider specific code, and that will
be addressed in a different commit/issue.