Updates for r34.

- All RP events are now prefixed with "rp" instead of "stonehearth".
- Instead of proposing a WorldGenerator object (which no longer exists), you propose a function that creates a BlueprintGenerator. This generator will then be used. All events have been renamed from "world_generator" to "blueprint_generator".
- Added rp.is_valid.
- resource callback handler patches have been removed. The addition of overlays and `stonehearth:is_harvestable` made them obsolete.
Removed personality_serivce and renamed entity_created event.