patch [#28118] Add XNA requirements to the official FBX exporter

from John Brown (jcbdigger)

The patch has been modified, some of the changes I rather see applied as separate patches.

This commit adds/changes:
- Option to export XNA compatible armature rotations.
- Option not to export mesh edges.
- Always export armatures as 'Limb' type.
- dont write default cameras or camera switch when cameras are disabled.
- fix for (harmless) error where armature connections were written out twice.