Remove processed count from MysqlCommand, track it in MysqlCommandSenderHandler.
Remove getResultHandler() from MysqlCommand hierarchy,  have all commands implement MysqlCommandResultProcessor directly.
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.
Moved closed connection check back into MysqlConnection, and exposed write/writeAndFlush() methods for executing MysqlCommand objects.
Merge remote-tracking branch 'origin/master'