Allow removal of items again.

The previous code assumed that controllers got selected, which was no longer true.
Fix exporting of models.

Again, the itemController was used even though the selection now contains only items.
Fix the underlying issue that caused #28.

Comments confused the later parts of the regular expressions and meant that a commented-out part in the mesh group declaration resulted in the mesh group declaration being no longer recognized. The fix is to ignore comments.
Fixes #28

Set the groups correctly, using the now-fixed parseItems tool. Similar issues may exist for other models, but I am not aware of any right now.