query_service: added support for admin statements

Support for SHOW, DESCRIBE, EXPLAIN and ANALYZE.
query_service: official PLAN_SELECT_STREAM plan id
Merge branch 'master' into parser
Add EnableSSL() to mysql.ConnectionParams.
Print start time when running integration tests.
Add connect_dict() to Tablet class to use DictCursor.
Use GTIDSet to specify replication position.
Merge branch 'gtid'
queryservice_test: revert the cleanup removal

Looks like some tests still rely on the cleanup of tables.
Merge branch 'master' into rowcache
queryservice_test: actually add the cleanup statements
Merge branch 'master' of github.com:youtube/vitess
Exponential backoff retry in VtGate client

Add retry for RequestBacklog error