[EXPERIMENT] Barrier avoidance
Merge branch 'master' into survival
Difficulty ramp
Fix spawn logic, only allow groups of 2 or 3
Add more spawner config
Fix spawn difficulty increase
Abstract spawner into mixin
Revert "[EXPERIMENT] Barrier avoidance"

This reverts commit 45654c4021070ba7b982972ebb6dac669457014a.

Conflicts:
	app/entities/spawner.js