Fixing concurrency on RPC calls with no param.
Now using time.Duration everywhere in rpcs.

We used to have times in seconds for some reason.
Refactoring vtworker binary to split split_diff.

Easier framework to make it trivial to add new commands.
Refactoring diff tools a bit.
Movign another function to its rightful place.
Fixing a couple issues in diff.

1. need to reset wrangler timeout before calling ChangeType.
2. using more local variables for state names.
Better diff report display.
Moving some topo code into a small library.
Calling vtworker in SplitDiff mode in test.
Implementing binlog player StartUntil.
Adding first version of environment.py for tests.
Moving generic topo server to environment.
Small fixes.
Small fixes to tests.
Some more test fixes.
Adding 'vtctl GetSrvKeyspace' and 'GetSrvShard'.

Using GetSrvKeyspace in resharding test instead of zk call.
Cleaning up this test.