A batch of collider usability improvements.

[Hoikas]

This addresses some common gotchas with exported colliders:

• Flat convex hulls (planes) are now forced to triangle meshes.
• Triangle mesh regions will cause the export to error on MOUL and Myst V mode because the physics engines in those games either do not support this combination or only partially support it.
• Triangle mesh regions now alert in the UI, where appropriate.

[DoobesURU]

After exporting, it appears that it tried to abort when it found one bad object with collision:

Writing Age data...

Exported 'ChisoPreniv.age' in 99.22s

Aborted after 99.68s
Error: HdnDoorButton: Physical wants to be a convex hull but appears to be flat (volume=1.7214252068242786e-07), forcing to triangle mesh...
DAG zero... not allowed to happen!
Error: HdnDoorButton: Physical wants to be a convex hull but appears to be flat (volume=1.7214252068242786e-07), forcing to triangle mesh...

EDIT: I should note that I was able to get things working by removing the "f" in the line mentioned above. Also, the object in question doesn't have a collision mod, but is referenced in a node tree, if that makes a difference.

[Hoikas]

Verified