BIG update: Added better object handling

- Collision and gravity can now be applied to all doodads and players.
- Camera is now dynamically following the path of the player,
this fixes all bugs where the camera would get misplaced & also provides
with a better flow in movement.
- Camera can be hooked to any object in the world, and several as well.
This allows us to seal off parts of the map etc.
- The player object (constructor) now dynamically adds itself to the
core.player variable. Allowing us to switch to a new player at any time.
- and more!