Fix double-click to rename not working
Fix double-click to rename not working

The quad list draws elements of a group recursively, but ignored
the double-clicked element that was returned by the recursive call.
That was the reason why double-clicking on non-top-level quads or
groups did not open the rename dialog.
This commit fixes that.

Resolves #29

25A0/Quadtastic,25A0/Quadtastic