Create special handling for duplicate faces on PSK import

[cmbasnett]

Some PSKs have duplicate faces (i.e., a face with the same 3 vertices as another face), and Blender does not allow this for technical reasons, so our addon discards them as "degenerate faces". However, duplicate faces does not necessarily mean redundant data, since the wedge info (material, UV etc.) can be different for each of the twin faces.

The cleanest and simplest solution is probably to be put these duplicated faces on a separate mesh. The only issue is that the shading will not be consistent because the new geometry would be isolated from its surrounding geometry.

[6yXJI0]

How did the previous importer handle this issue? The one I dropped earlier

[cmbasnett]

I'll have to look into how and if it handled it. Might be able to just replicate it as long as its sensible.