- remove old listeners when updating treecell item. cleanup GroupTreeCell
- invalidateHashSetHitsCount before adding/removing files to make sure it is seen during listner involation
- cleanup GroupTreeItem and NavPanel
- add comment to GroupManager
For speed, now stores hash set hits in memory.
Fixed bug where hash hit count would never update after a group was created, even if files were added/removed
Changed category zero count to be bases on other counts and not stored separately.
Changing sort method and ascending/descending now updates the GUI immediately.
Properly decrement uncategorized file count.
Fixed a few case-closing exceptions.
