Adds recognition of triangle geometry and index list offsets.

[bigtimecriminal]

• Geometry parser will read 'triangles' geometry list.
• Geometry parser will read using index list offsets, not assuming index order.

These changes are intended to make the tool compatible with triangulated meshes and meshes produced by the godot collada exporter: https://github.com/godotengine/collada-exporter

[chinedufn]

Hey thanks for submitting a PR!

I see that you've closed it, any reason why?

Thanks!!

[bigtimecriminal]

I don't think the way I read in normal info is valid for some Collada meshes. I'll work on it this week and resubmit.

[chinedufn]

Gotcha!