Added some things

Added Obstacles: satellite and Comets to impede your progress. They are their own set of objects, however they might just become part of the astroid objects later.

I also added a level variable so that the game can be longer (elevation would otherwise max out at 32000),   It will likely be used to help create the ending. I'll later use it to increase the games difficulty.

Added a timer to help encourage the use of the booster.