Automatic merge from submit-queue
Allow etcd to store protobuf objects
Split storage serialization from client negotiation, and allow API server to take flag controlling serialization.
TODO:
* [x] API server still doesn't start - range allocation object doesn't seem to round trip correctly to etcd
* [ ] Verify that third party resources are ignoring protobuf (add a test)
* [ ] Add integration tests that verify storage is correctly protobuf
* [ ] Add a global default for which storage format to prefer?
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