Fix strange resume_data bug causing fastresume not save on shutdown
[#1859] [GTKUI] Improve layout of Remove torrent dialog

 * Using Shift+Del will now pre-select removing files.
 * Will now show the name of the individual torrent being removed or the
   total count if multiple torrents selected.
[#2347] Add orig_files to core
Refactor and tidyup code in torrent.py