In this situation, the script creates a dummy root bone... But code was buggy (and import of non-rotating bones was too).

finished

also use less confusing bone rotation matrix -> euler conversion on export.

Plus a few styling enhancements.

[[Split portion of a mixed commit.]]

- add option to export root transform only (may help with secondlife compatibility)
- operators are now pep8 compliant.
- frame is set back to the original when export is done.

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

was missing undo push as Joshua pointed out.

zero length bones had their tail offset in the wrong direction.

most editors (besides notepad) will open these files without trouble.