Made the client & server compile, linked box2D, added some classes & integrated them to the client.
Added a world loop class to the server & some new config options in the config file.

The Entity-code will be migrated to this external class (runs in an external thread), because the main thread on the server is blocked by the network stuff.
Introduced a /stop command (for everybody - going to change that soon xD), server is now running a game-loop thread correctly.

The game loop runs at a standard of 60 ticks per second - this is configurable through the XML config file though.