Use correct item id
Replace A* implementation

The previous A* implementation crashed the server by illegal memory access.
Switched to implicit A* in boost 1.52.0. Patched luabind to work with newer
boost versions under gcc. A replacement for luabind needs to be found soon.
Fix monsters' path to targets
Remove counter and param from entrypoints as well as target item from UseItem
Fix and limit pathfinding
Add safety check to limit depth
Adjust pathfinding for monsters
astyle
Refactor MapVector: hold maps in private member
Refactor MapVector: store maps in shared_ptr

Also remove some outdated map related code like roofmaps
Refactor MapVector: rename to WorldMap
Refactor WorldMap: looking up a Field is now a constant time operation