Improvements made during LD 30

These are the changes that were necessary during the Ludum Dare 30
compo:
* Entities implement ILevelProvider.
* Tiles got a "removeOnCollision()" method. If it returns true on a
collision, the tile will then be removed. Temporary solution!
* The Game class got a pre-initialized Random instance.
* Filter changes. These include: Display returns number of filters
applied, Filter class returns the (modified) input image, FlipFilter was
added.
* Characters '=', '(' and ')' were added to the LineFontRenderer. Also,
it now resets the Identity after drawing.
* The ShapeRenderer can draw simple lines ([x1, y1] -> [x2, y2]).
* A TextureIcon GUI component was added. It displays a texture inside a
GUI environment.
* The ILevelProvider interface now requires you to define the type of
level that it returns. This makes it easier to use (casting is not
needed anymore).
* Levels have functions for getting the offset.
* Tiles get the Level instance in which they're located when methods are
called.
* Tiles also have a collision representer now, instead of an anonymous
inner class. This means you can now interact with them when collisions
happened.
* TiledLevel received methods for mass-adding of tile mappings, as well
was methods for getting the dimensions (tile amount, not pixel amount!).
You can also set tiles now.
* Vectors now can be modified with x and y parameters, instead of
another Vector.