Extend storage mechanism/indexing/retrieval for supporting high-res features

[oubiwann]

Houses, mansions, castles, towns, cites, cave systems, etc., could all be stored as raster images, each of the features supporting multiple layers. However, these would be at a much, much smaller resolution than a single pixel.

It seems like we might need to extend the bit layout that was proposed in #25 (comment) ...