Remove PEContext, now that execution only involves a handful of threads.
Fix obvious resource leak in tests, tightened up resource cleanup in backend decoder.
PE-1512 - Enable SELECT mirror test in testPE1512().
Reduce transient test failures due to execution timing when timestamp set to DEFAULT.
Merge branch 'master' of github.com:Tesora/tesora-dve-pub
Split writeCommandExecutor() call into separate segregated interface, streamline some internal execute usage.
Pull StorageSite and DBConnection.Monitor from writeCommandExecutor() call, since these can be picked up during dispatch/visit.
Changed DBResultConsumer to abstract base class and made it responsible for dispatch/visit logic previously in MysqlConnection.
PE-1632 - Added comment length checking to the parser.

Extended the ExpectedExceptionTester to ExpectedSqlErrorTester which can
be used to verify SQL error codes (ErrorInfo) carried by our exceptions.
Removed preemption logic, so all backend requests/responses are FIFO with no overlap.
Changed it so decoder could signal request end in the protocol objects, and removed isDone() from the command/results processing.
Merge branch 'master' of git@github.com:Tesora/tesora-dve-pub.git
Moved assertError logic from PETest into PETest.ExpectedSqlErrorTester
which also asserts the exceptions.
Remove processed count from MysqlCommand, track it in MysqlCommandSenderHandler.
Cleanup assertError code.
Remove getResultHandler() from MysqlCommand hierarchy,  have all commands implement MysqlCommandResultProcessor directly.
PE-1632 - Improved unit tests.
Removed DBConnection.Monitor from MysqlCommand.execute().  It was only used by MysqlExecuteCommand, which can get it at construction time.
Move promise success for commands that don't expect responses into command.
PE-1629 - Drop the NO_AUTO_CREATE_USER mode. Add FLUSH PRIVILEGES around
CREATE USER.