Graphics -> Production

Many updates:
- New preferences file, with (hopefully) correct naming and the Javadoc warning
- Added MockSprite, which you should use to sever links to the Graphics system when testing Entities (issues with the links between the systems will be uncovered during integration testing, which is imminent)
- Implemented additional functionality in the Graphics class, in preparation for creating integration tests, and added more tests
- Added World interface, which is needed by Graphics and Controllers (and almost certainly Networking). Model team remains responsible for implementing the actual concrete class.
- Added Controller interface, which I need to create a camera controller.
- Added some missing TankSprite tests, and simplified some of the tests