Added possibility to reserve maps

If you set net_gameServerName you can now reserve maps in the maps.xml.
There you have to add the servername - property to the <map> tag.
Then the map will only be activated by that server.

Also changed the activate sequence that the account server now tells the game
server what maps to activate (previously the server requested all maps and the
account server said yes or no).

TODO: Fix general inter server map switching.
Fixed default value of the servername

Since the name was used to log things and the default now is "" also added
logging of the address and port too.
Added Debug class for more convenient debugging output

Inspired by the QDebug class and qDebug() function from Qt. Actually it
might be nice if the LOG macro would also use this.