Completion of the multiplayer mode.

A standard multiplayer mode should now be working. The server keeps
track of who wins etc. and the players are taken back to the multiplayer
menu after the game.
Merge branch 'develop' of https://github.com/linlind/Shotris into develop

Conflicts:
	Shotris/src/engine/GameLoop.java
	Shotris/src/engine/GameState.java
	Shotris/src/graphix/drawing/GameSideBarCanvas.java