add a seventh illusion to Optical Illusions
fix RGB primitive description
fix doc for HSB primitive
minor User Manual tweak
update FAQ to cover Android too, not just iOS
'export-world' now catches 'IllegalStateException's

Fixes #267
Merge branch '5.0.x' into topic
fix performance issue with task creation (fixes #255)
Merge branch '5.0.x'

Conflicts:
	src/main/org/nlogo/nvm/ExclusiveJob.java