Blender Git Loki

[#22488] Reloading scripts causes crash
F8 key enabled again, useful for script UI development.

- keying set freeing wasnt freeing from all scenes and the builtin list.
- PointerProperty() cant refer to a removed python srna type (fixed in rigify and netrender).
- Added a check for freeing a type used by a PointerProperty but its very slow, makes reloading take ~10sec. Only enabled this in debug mode for now.

Netrender register() function isnt re-registering the property, probably because the module is cached by python and not re-run.