Support mesh groups 36-37 from XPS

[cochrane]

The only documentation I could find was this: http://junkymana.deviantart.com/art/XNALara-XPS-Render-Groups-543000260 Eh, good enough, I guess. Now I just need to find some models that use them.

40 and 41 are not included because as of 97f5b43, they're already supported. In that case I had a test file.

[cochrane]

Update for others who are wondering: The canonical list for the render groups is currently at http://xnalara.home-forum.com/t225-lession-9#1938

I wouldn't say it answers all questions (what does the "Shading" column do?), but it's at least something.

[cochrane]

38, 39 are done, but it turns out they're already up to 43. So remaining right now should be:

36, 37
42, 43

[cochrane]

Forgot to mention it in commit message, but 7e765ab adds support for 42 and 43, leaving only 36 and 37.

[cochrane]

The documentation I found in 2017 has now moved to http://xnalara.forumotion.com/t225-lession-9#1938 I really gotta write my own somewhere so I don't have to rely on this…

[cochrane]

Quick note: The reason why I haven’t implemented the two missing groups is because I have no models that use them to test.