This makes it possible for hierarchies to clean themselves up (by
deleting their entities (though that will cause other problems later
when the hierarchy doesn't own the entities)), thus plugging a memory
leak when parsing passage text.
The main goal of this change was to make it easier to tell when a
hierarchy has been deleted, but as a side benefit, it got rid of the use
of PR_RESMAP. Also, it's easy to track the number of hierarchies.
Unfortunately, it showed how brittle the component side of the ECS is
(scene and canvas registries assumed their components were the first (no
long the case), thus the sweeping changes).
Centerprint doesn't work (but it hasn't for a while).
They're not quite working (trail path offset is incorrect) but their
pixels are getting to the screen. Also, lifetimes are off for rocket
trails in that as soon as the entity dies, so does the trail.
