Added regions to the Game class.

* Game.cs:
  Added regions.

* SpaceTapper.csproj:
  Removed -help switch that was left in from the previous commit.
Added initial implementation of the block spawner. Misc changes.

* Block.cs, Difficulty.cs, BlockSpawner.cs, IResetable.cs:
  Initial version.

* Vector2.cs, MathUtil.cs:
  Moved from Source/Math.

* Entity.cs:
  Added IResetable interface & implementation.
  Added default return for GlobalBounds.

* Player.cs:
  Fixed namespace.
  Added Reset() method.

* Game.cs:
  Added static Random variable.

* GameScene.cs:
  Added InProgress variable.
  Added BlockSpawner entity.
  Added StartNewGame() nad EndGame() methods.

* Scene.cs:
  Changed default active status to false.