vtgate v3: planbuilder unit tests complete
vtgate v3: planbuilder cleanup
vtgate v3: add tests to cover new code paths
vtgate v3: remove currently untesttable code

v3 api doesn't get along with the existing keyspace_id
scheme in tablet manager. This means that we can't
integration test the VTGate entry points. So, it's
better if such code is removed.
Merge pull request #146 from youtube/vtgate

Vtgate