Adding event package for pluggable global event listeners.
queryservice: Fix & improvements to comments parser.

The comments parser had a bug where it would fail to
detect comments like this: /** ... */. This CL fixes it.
I've also the panic scheme of handling failures.
The resulting code is longer, but more readable.
I've also written more tests to cover the corner cases.
Adding a TabletOption interface for options on the tablet.
Move test utility function to _test.go file.
Unit tests now close topology.
Merge branch 'event'
Adding syslogger plugin for event package.
Merge branch 'master' into vtocc
queryservice: expvars SpotCheck* -> RowcacheSpotCheck*
sqltypes: remove compiler bug workaround
Adding more granular stats, using them in vtgate.

The Timings stats collection only had one dimensional
keys, now adding one that supports multi-dimentional keys.
Using it in vtgate for incoming and outgoing stats collection.
Fixing unit tests to not all export the same stat.
Reducing verbosity of mysqlctl output.
Adding stats.MapCounters, similar to MapTimings.

Using it in vtgate error counting.
Adding comments to some methods.
Using MapCounters, retiring Matrix.
Using MapCounters for vtgate topo counts.
Not forking mysql to execute an admin command any more.

Or it fails with a credential server. It means we have to export
the dba queries out of mysqlctl, not a big deal.
rowcache tweaks

Don't allow rowcache without strict mode
Start invalidator after schema is initialized
Reword strict mode description
Merge branch 'rowcache'