2101 - Collision grid data and input maps

I was thinking of a case I’d like to try that would make option 2 problematic: Intentionally fully overlapping objects. e.g. a shield around a ship. Which makes the case for option 3. So, we’ll start with that. (Although as I said earlier, revisions on various speeds, sizes, and spawn frequencies may change the situation enough to require a completely different solution.) Start by creating collision_grid. We’ll hook this up to enemy_instances, hero_instances, enemy_bullets, and hero_bullets to get grid data for each of them respectively. To hook them up, we’ll map collsion_source_instances and collision_source_types. I decided to simplify the mapping process a bit for when I don’t specify a source (i.e. when the offsets in the map are assigned at runtime.) But to do that, I need to fix up the builder scripts a bit. TODO: Need to support importing schemas in schemas, to look up types. (Without source data, we can’t infer the type anymore.) Bullet and hero/enemy type data store radius in different formats (radius_q8 and radius_q4, respectively.)