[F2] Adds UV support and triangle caps

- UV information is now preserved when adding new faces
(interpolating UV coordinates). This can be switched off
in the user preferences.
- Quad strips can now be finished with a single triangle.
Merge remote-tracking branch 'hm-blender/master'

* hm-blender/master:
  [F2] Adds UV support and triangle caps
Code cleanup: style
Fix T39629: Teapot creates corrupt mesh

more of a workaround, at least stops crash.
Error in recent commit
FBX: Some minor cleanup, and pep-8.
FBX: add support for baked animated armature export.

Note: tested on unity & houdini with some basic mesh/rig, needs some more serious testing with real animated characters!
FBX: Looks like I was still missing something in axes 'encoding'...
FBX: Fix (bones) animation: Looks like it's better to only have one layer per animstack for now.

Even if they do not affect the same properties, multi-layers interactions are rather complex.
FBX: better handling of baked rotations (use euler_compat stuff to avoid gaps in rotations).
FBX: Add option (enabled by default) to export each strip from NLA in a separated baked animstack
(in addition to global anim from scene).
FBX: Add support to export other geometries (curves, metaballs, etc.) as meshes, and implement the 'apply modifiers' option.
FBX: add support for more FBX freamrate modes, since stupid Unity does not hanle 'Custom' one.

Should fix Unity timeline weirdness (as long as you use standard framerates like 25fps, 30fps, 29.97fps, etc.).
FBX: tweaks from user feedback & for Unity compat:

* When exporting actions from NLA, do not export global 'scene' action (unless there is no actions in NLA!).
* Export actions from NLA as all starting from 0.
* Fix take time to be one frame longer than the longest animstack exported.
Merge remote-tracking branch 'hm-blender/master'

* hm-blender/master:
  FBX: tweaks from user feedback & for Unity compat:
  FBX: add support for more FBX freamrate modes, since stupid Unity does not hanle 'Custom' one.
  FBX: Add support to export other geometries (curves, metaballs, etc.) as meshes, and implement the 'apply modifiers' option.
  FBX: Add option (enabled by default) to export each strip from NLA in a separated baked animstack (in addition to global anim from scene).
  FBX: better handling of baked rotations (use euler_compat stuff to avoid gaps in rotations).
  FBX: Fix (bones) animation: Looks like it's better to only have one layer per animstack for now.
  FBX: Looks like I was still missing something in axes 'encoding'...
  FBX: add support for baked animated armature export.
  FBX: Some minor cleanup, and pep-8.
  Error in recent commit
  Fix T39629: Teapot creates corrupt mesh
  Code cleanup: style
FBX: fix some bugs and glitches with animations...
FBX: user request: check for vertices used by/assigned to more than four bones.

If new option "Simplify Skinning" is set (by default), only four most significant weights are kept.
Else, only a warning is issued.

Also added more OrederedDict's!
FBX import: fix for newest FBX format (>= 7.4) using no more leading 'K' in templates' type names.
FBX export: fix handling of mesh instances.

Was broken since apply modifiers and other geom types support was added.
Merge remote-tracking branch 'hm-blender/master'

* hm-blender/master:
  FBX export: fix handling of mesh instances.
  FBX import: fix for newest FBX format (>= 7.4) using no more leading 'K' in templates' type names.
  FBX: user request: check for vertices used by/assigned to more than four bones.
  FBX: fix some bugs and glitches with animations...