Prep for horizontal split copy worker: find overlapping shards.
Making MigrateServedTypes use the new overlaping shard code.
Adding first non-working version of split clone worker.
Adding split clone vtworker test.
Merge branch 'master' into replication
Adding row splitter, now resharding_vtworker.py passes.

Still needs some cleanup.
Adding test for row_splitter, minor clean ups.

Now vtworker horizontal split is fully functional.
Merge branch 'master' into replication
Merge commit 'c4bd0013e035f19da398ae9d5942df5c1dee4d9c'
Merge branch 'replication'
Refactoring a bunch of code in worker. No functional change.
Refactoring some RPC code, so other RPC implementations can use it too.
Merge branch 'master' into replication
Now using pointers for TableDefinition lists.
Migrated the tests to use vtgatev2 instead of vtgate.
removed vtgate_test from Makefile.
Converted these two tests to use vtgatev2.
Fixed the BatchCursor to use the correct api for execute.
Removed v1bson protocol and its usage.
Fixing this unit test.