Added brick texture
Added treasure texture
Merge branch 'master' of https://github.com/Freezerburn/cmsc425-loderunner into vineet/graphics
Added door texture and temporary background
Added ladder texture.
Added preliminary level 2
Moved camera logic out to a trait
Camera now stops at all level boundaries

Be warned, however: if the level boundaries are small enough, the camera will
bug out slightly and allow the player to see beyond (0,0). Please see the size
of LevelOne for (almost) the smallest size you can make a level horizontally.