Message log

Implements message logging to database as requested in #469 
Most of the reference for this implementation is in the issue at this comment: https://github.com/Cockatrice/Cockatrice/issues/469#issuecomment-65955174
This is the dump of the "log" table filled with example data:
```
--
-- Table structure for table `cockatrice_log`
--

DROP TABLE IF EXISTS `cockatrice_log`;
CREATE TABLE `cockatrice_log` (
  `log_time` datetime NOT NULL,
  `sender_id` int(7) unsigned DEFAULT NULL,
  `sender_name` varchar(35) NOT NULL,
  `sender_ip` varchar(255) NOT NULL,
  `log_message` text NOT NULL,
  `target_type` enum('room','game','chat') DEFAULT NULL,
  `target_id` int(7) DEFAULT NULL,
  `target_name` varchar(50) NOT NULL,
  KEY `sender_name` (`sender_name`),
  KEY `sender_ip` (`sender_ip`),
  KEY `target_type` (`target_type`),
  KEY `target_id` (`target_id`),
  KEY `target_name` (`target_name`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

--
-- Dumping data for table `cockatrice_log`
--

INSERT INTO `cockatrice_log` VALUES
('2015-01-01 16:40:00',1,'ctrlaltca','127.0.0.1','message from a REGISTERED user to a room','room',0,'General room'),
('2015-01-01 16:40:23',1,'ctrlaltca','127.0.0.1','message from a REGISTERED user to a game','game',6,'test game'),
('2015-01-01 16:40:58',NULL,'Player_1','127.0.0.1','message from an UNREGISTRED user to a room','room',0,'General room'),
('2015-01-01 16:41:05',NULL,'Player_1','127.0.0.1','message from an UNREGISTRED user to a game','game',6,'test game'),
('2015-01-01 16:41:23',NULL,'Player_1','127.0.0.1','message from an UNREGISTRED user to a REGISTERED user (chat)','chat',1,'ctrlaltca'),
('2015-01-01 16:41:33',1,'ctrlaltca','127.0.0.1','message from an REGISTRED user to a UNREGISTERED user (chat)','chat',NULL,'Player_1');
```

In servatrice.ini new configuration options have been added to enable/disable logging of room messages, game messages, private chat messages and messages coming from other servers (ISL)