Fixed error checking in behavior so it happens before crash.
Added ability to create objects with behaviors, and made GameObject final to avoid accidental errors.
createBehavior now returns a reference to the created behavior, get returns it in the correct type, fixed docs in gameobject.
Fixed returns of createBehavior.
Fixed returns in the other createBehavior.
Fixed non-shared return type in Behaviors.get.
Fixed default materials
Merge branch 'release/v0.7.0' into develop