3 different ban methods (Name, IP, GUID)

Full Changelog:

- Each ban method is now saved to it's own file (due to some issues);
- Added a CHAT LogLevel to Log.cs that is Yellow
- Readapted the ban command so now it is split into 3:
*/ban [player]
*/banip [ip]
*/banguid [guid]
- Added 2 new functions on ClientHandler: GetClientByIP() and
GetClientByGuid();