Lot of improvements / cleanup. Read description.

- Changed the highlights to a single prefab. A script now changes the
highlights sprites. Via a ChangeHighlight method you can change the
highlight which needs showing. This monobehavouir is hold in the list of
active highlights.
- Eventhandler class. (Copy of marauders project, shhh don't tell. :P)
Right now fires three events. On-Unit, Building, Highlight click.
- Highlight, movement, attack and unit production now use the event
system. Which cleans up ALOT of code. So clean, very awesome. Much
better.
- Moved some variables from Gamemanager to highlight, movement and / or
attack. Since they need to keep track wether for example NeedsMoving is
true of false.
- Fow is now updated during unit movement.
- Instead of tracking a Tile object,  a unitgameobject is now used for
the highlight, movement and attack class.
- Some minor refactors in unit, building, factory classes.
- Deleted the Levels folder since it is not used.
- Some fog of war improvements.
- Cleanup up alot of classes with unused code and comments. Especially
in GameManager.
- This was it i think.