Added concrete GameWorld class

GameWorld implements the World interface, which is necessary for the
rendering system.
Added CameraController

- CameraController interface
- TankCameraController implementation, which moves the camera based on
the position of the tank
- Updated World with getMapWidth and getMapHeight methods, which are
needed by TankCameraControllers
- Update GameWorld impl based on World interface updates
- Added Graphics.addCameraController method
Implemented tests for CameraController & GameWorld
Fixed problems w/ GameWorld
Increased test coverage
Created two packages

- bubolo.controllers.input
- bubolo.world.map
Added TankSprite; getInstance() static method to Graphics

- The Graphics.getInstance() static method is only accessible to the
graphics system, and it must not be called before the Graphics class is
explicitly instantiated.
- Enables all graphics classes to access the Graphics system, even if
they don't have a reference to it
- TankSprite now sets the tank camera controller. However, it will need
a way to determine if the tank is the local player before it works
properly.
- Added additional tests
Added main game class and loop

- Main game class: GameApplication
Fixed FindBugs issue in Graphics
Added tests for GameApplication

Also synchronized LigGdxAppTester
Added additional sprite.create overloads

Also added tests for the overloads
Merge pull request #32 from BU-CS673/Canfield

Canfield -> Graphics
Merge pull request #30 from BU-CS673/Aaron

Aaron -> backend
Merge pull request #33 from BU-CS673/graphics

Graphics -> Production
In the process of modifying TankSpriteTest, which is failing after merge.
Added Graphics constructor to TankSpriteTest, was failing when run on its own!
Modified package structure to make world classes easier to find. Removed
parametric Entity constructors and replaced with a setParams method.
Moved unit testing default parameters to EntityTestCase and reworked all
Entity unit tests to be more concise. Moved all Entity unit testing over
to MockSprite and removed DefaultSprites from current use.