Remove excessive waiting in kubelet etcd loop

Listen to etcd longer, and wait a shorter time before reconnecting.
No longer an argument to the source.
Allow field/label users to get info from fields

Allows a consumer to get at the information stored in the field selector
for querying an underlying data store.  Not generic, but offers a
simple start.
Move EndpointsController to its own package

Avoids recursive loop with endpoint registry defined
Expose REST resource for endpoints and watch on services/endpoints

Will allow kube-proxies to listen on endpoints.
kube-proxy can read config from the apiserver

All clients that talk to a "master" as a host:port or URL
(scheme://host:port) parameter.  Add tests.