Battle system

As the title says, adds a partly working battle system :).
Please don't merge it yet. I just ask you to test (and crash) it \*g\*

Fixes #81
Fixes #110 
Fixes #117 
Fixes #178 
Fixes #192 

Also fixes graphic issues with Battle Animations and allows using healing Items/Skills (and similiar stuff) in the Menu.

Issues found that must be resolved before merging:
- [x] Crash when loading a game
- [x] Win soundeffect plays endless on Map in RPG2k3 after battle

Missing features I will NOT implement in this version:
Battle Commands: Link to event, Defend, Double attack
Enemies: Escape, Defend, Charge Up, Self destruct
Different battle layouts (RPG2k3 only)
Handling conditions (Except Dead)
Properly working Event interpreter