Clean up heuristic logic

* Disable/enable sensors and their heuristics together
* Clean up logic for drawing sensors - update paint at each call to
  sense() and let all other tasks (enable/disable drawing) be handled by
  the portrayal itself.
* Make the heuristic schedule set itself in heuristics that are
  scheduled.
Add static friction and tweak friction parameters
Add Khepera III phenotype and sensors

Conflicts:
	build.gradle
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