Add several game modes

[Bluenix2]

Currently there is only this one level wave mode. This could get expanded upon with a lot more levels.
But there could also be a endless mode where random wave presets are picked.

Additionally a moving mode, where the bricks slowly move downwards could be implemented. This would give a more of a time rush for the game. As with the other one, a level based and high score based "sub-mode" could be implemented.