Graphics -> Production

The following is included:
- Ethan added many new images
- Ethan added PillboxSprite and RoadSprite
    * PillboxSprite needs Pillbox to be implemented so it can check the pillbox's health
- TankSprite is now animated
    * It is currently always animated. I'll fix that in the future, so that it will only animate when actually moving.
- TankSprite loads different texture regions depending on whether the tank is local or not
    * There are a number of TODOs that will be addressed when isLocalPlayer()/isLocal() is available in Tank. There is also some commented-out code that is related to that.
- GrassSprite is now fully implemented, and uses the correct texture
- Removed concrete Grass and Road dependencies from GrassSprite and RoadSprite, since Entity has everything they need
- Switched Sprint1 class to use OpenGL ES 2, which eliminates need for power-of-2 textures
- Fixed many graphics unit tests that broke after switching the OpenGL version (these may no longer need the AllGraphicsTests test suite, though I'm leaving it for now)