Fix mesh export bug

[stig-atle]

Not all geometry with modifiers and editing gets exported the way it should. Fix so that we are sure the mesh \ depgraph is updated, so that it exports the final geometry.

Typical example of the issue is seen here:

[stig-atle]

So, the issue boils down to this: Apply a 'triangulate' modifier, and then a 'edge split' modifier - the problem is resolved. Now I have to figure out how to do that on export, without messing up the original mesh. Kinda like taking a 'snapshot' with the resulting mesh, then export that.

[stig-atle]

apply a triangulate modifier, and split edges modifier makes it export the way I expect, now I need that result without adding modifiers while exporting.

[stig-atle]

Fixed by rewriting the geometry export code. I now export only tri's, through the use of 'loop_triangles'.