Class for computer controlled humans.

Given a array with all the zombies the human flees in a "proper" way.
Class for computer controlled zombies.

Given a array with all the humans the zombie picks the closest one
within a certain range and starts to move towards her.
Use the "world to box" ratio given in the Contants class.
Implemented a simple testing screen.

Modified GameScreen for the use of some simple testing of the AI.
Removed debug code.
Merge branch 'zombie-human-ai' into develop