Pathfinding initial commit

This change adds pathfinding (A* algorithm) to the player (GameCursor, LabCursor, PaintBrush, SolderPen) when clicking.  Particularly useful for wiring using the mouse as well as just moving around in the maze.

Just because I was worried about wearing out my arrow keys playing/testing DroidQuest :)

This is the initial version.  Future possible enhancements include changing double click to find the nearest exit to the click (within a certain range), as well as possibly changing right click to move & activate/pick up.