New sensors, new states

Added three new sensors
- Compass: Gives absolute orientation in the environment
- GPS: Gives absolute position in the environment
- EnvironmentSize2D: Gives the width and height of the environment

These sensors were needed for the new behaviors in
DomWorldStateMachine:
- Roam:	Heads in a random direction until it hits a wall, then
		follows the wall until a timeout. Replaces RandomWalk
- GoToWaypoint: Picks a random location in the environment, and
		goes there. Not used in the state machine yet.

I also moved the states into their own named inner classes, as the
constructor was getting messy.