Proof of concept of using a dot per sibling in metadata 

Similar to DVV but without changing object storage format. Uses a
dot in the sibling metadata. Breaks the ec_eqc test (natch)

Only opening the PR for discussion. Here are the problems as I see them:

1. Client ids
2. https://github.com/basho/riak_kv/issues/679
3. Do we have the test coverage to verify this really works?
4. I borked the tests we have

Interested if anyone has time to help me get this into 2.0

NOT READY FOR MERGE, JUST FOR DISCUSS

See the riak_test at feature/rdb-sib-ex.