TVrank cannot handle the cancellation of database downloads

[fredmorcos]

TVrank leaves behind semi-complete files when the database downloads are cancelled. The current workaround is to delete $XDG_CACHE_HOME/tvrank/* and re-run TVrank and wait for the downloads to complete.

TVrank should instead detect that the user is canceling while downloads are running, and clean up after itself: either by deleting whatever has been downloaded and processed so far, or finding a way to resume from that during the next run.