* Added reassign_letter()
* Attempts to reassign a volume to better ensure predictable letters
* i.e. Local Windows source volume letter == 'I'
* Adjusted code to avoid the "hidden" assign_volume_letters() call in select_disk()
* Added set_title() which sets window title and global_vars['Title']
* menu_select() will now display global_vars['Title'] above title
* (If it exists)
* Bugfix: fixed a few bad calls of menu_select()
* Split backup.py into disk & backup
* disk.py is for lower level disk management
* Renamed functions\data.py's select_disk() to select_volume()
* Avoid name collision with functions\disk.py's select_disk()
*
