Added some squared distance methods to aid optimization

regarding looped distance calculations
Optimized RangedAI.checkForEnemies()
Rewrote Door.java to make use of propertyFlags and omit functionality regarding locked door (which should be a class of its own).
Removed IS_INDOORS property.

Flying creatures are no more permitted to fly above walls: They should
be rather though of as levitating, only allowing them to hover over
lava and water terrain etc.
propertyFlags is now initialized in each sub class constructor, listing every propertyFlag used by the class, thus making things clearer.
Improved MabObject.dealDamage(int)
Merge branch 'master' into quadtree
Added comment regarding QuadTree children node storage.