Keyboard Controls

[ArztKlein]

Added keyboard controls which resolves #23.

I added the keyboard controls which @alin256 mentioned

toggle bias to a large key such as the space key pause action for e.g. the escape key.

And also backspace to pull the drill back

Minor changes:

• When the game is finished, the aiming arcs are hidden
• Renamed 'steering limits' to 'steering aim'