[STABLE] Massive Structure Change

There is now a world object. This is in preparation for universe loading
(universes contain world level sets, which have any number of levels
iterating from 1 to any number). The Level select interface is about to
be underway and the camera is being slightly rebuilt. Physics have been
moved around, and a lot of interactivity logic between the map and
player have been moved.

Map loading is starting to become finalized as the level selection is
getting closer to completion. One thing to note: text files are now
unsupported as a map file type. This may change once image types are
finalized, but for now, I see no other way to do tube travel with my
game structure without going overboard on map text complexity in both
creation and parsing.