Add richer counters for GetEndPoints vtgate call.

We want counts split-out by cell/keyspace/shard/dbtype. We also want to
count stats based on what was returned regardless of what was in cache.
In this way, we can reasonably estimate for example, the rate of queries
served errors; this is a better monitoring strategy than reporting
whether there would be an error were a query to be served at the time of
stats poll.
Rearrange on-return stats counting to better count remote entries even if they are errors.
Moving a couple files from wrangler to topotools.

They fit better there, as they don't use the wrangler anyway.
Fixing this test too.
Merge pull request #75 from plobsing/count-vtgate-endpoint-queries

Count vtgate endpoint queries
Better doc and interface definitions for these files.
Merge branch 'master' of github.com:youtube/vitess
Adding a unit test for topology.
rowcache: change memcache_stats to poll

memcache_stats used to pull expvar values on demand. This introduced an
rpc dependency on expvar, which is not sound. With this change we
regularly pull stats from memcache and update the expvars.
Also, the new version has made the items & slabs stats optional, and
rowcache doesn't export them any more.
Merge branch 'rowcache'
Lowering the number of concurrent aciton nodes.
Add --max-in-flight argument to vtgate.

This is a means to limit the amount of queueing which can occur, which
should cause failure states to report as such faster rather than
becoming sinks for queries.
Fix queryservice tests for MariaDB.
Merge branch 'master' of github.com:youtube/vitess
Adding a Close method to VtctlClient, it's better that way.
Couple small fixes to these tests.
Fixup unit test.
Add new client-side error type to represent request backlog errors.

fixup
rowcache: add timeout for memcache

Memcache connections can hang under system duress. Adding timeouts
to make sure we can recover if stuff like this happens.
Also, connections are now closed if there is any kind of low level
error. This will allow the connection pool to replace them.
Refactoring this file a bit to allow for easier move.