* Property update functions no longer get context, instead they get only
Main and Scene. The RNA api was intended to be as context-less as
possible, since it doesn't really matter who is changing the property,
everything that uses the property should be updated.
* There's still one exception case that use it now, screen operations
still depend on context too much. It also revealed a few places using
context where they shouldn't.
* Ideally Scene shouldn't be passed, but much of Blender still depends on
it, should be dropped when we try to support multiple scene editing.
Change was planned for a while, but need this now to be able to call
update without a context pointer.