simplify the face structure; now, "fragments" just mean the output windings (if you opt out of tjunction fixing, then there will only be 1 fragment with the same values as original_vertices)
move MakeTangentAndBitangentUnnormalized to qvec.hh since we will use it later
-tjunc allows for more fine-grained control now (-notjunc still exists)
-maxedges now throws if you specify a bad value (1 and 2)
remove the checks to OmitFaces - we can tell if a face was omitted because it will have an empty winding
remove static variables from tjunc
fix tjunc multithreading; added `original_vertices` which is a copy of the `output_vertices` that is safe for tjunc to read from since tjunc writes to the former
- currently uses naive brute force approach to finding vertices on faces
- simplify 'face fragments', which now only need to contain vertex indices since they are already emitted