Also created a proper World struct in the process, to store all
infinite-extent type stuff.
Note that I goofed and did a new rustfmt pass but forgot to
commit before making these changes, so there's a lot of
formatting changes in this too. *sigh*
The lighting is super crappy, and pretty much hacked in. Will
need to redo this properly soon. However, this verifies that
certain other parts of the code are (mostly) working properly.
The AssemblyBuilder is responsible for collecting the data needed
to actually create an Assembly. AssemblyBuilders are now the
only way to create an Assembly, which guarantees that Assemblies
aren't half-baked.
Also got instancing working with transforms and such. It may not
be _really_ working because I don't have a complex test case for
it yet. But that will come later.
Includes:
- More scene parsing code. Making good progress!
- Making the rendering code actually use the Scene and Assembly
types.
- Bare beginnings of a Tracer type.
