Plus a few styling enhancements.

[[Split portion of a mixed commit.]]

- added default options for unity3d, can add other defaults too

gives a few % speedup

from John Brown (jcbdigger) 
patch file:
    fbx_xna_unified-2011-08-02a_jcbdigger.patch


Option not to export Default Take

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.

previous order deprecated.

- remove/comment unused variables
- remove unused imports
- fixed some bugs using incorrect variables

also write out deformed meshes as parentless since the bones `own` them.

also option to export lamps was missing.

Added option for smoothing export - Face/Edge/Off.