Scanner hanging bug

Currently (at least for me), the scanner hangs and never finishes when if it encounters any files whose names cannot be resolved to movie titles. The code gets stuck in an infinite loop at line 154 of manage/main.py as the movies are never removed from the "to_go" it loops indefinitely.

The fix is rather crude currently, and I am happy to improve it. I don't personally mind looking through the log for the files which failed so that I can rename them, but others might. I've arbitrarily notified the user up to 3x that a movie failed to parse, in hopes that they will notice, but it may be better to just put a message by the progress bar. If you have any thoughts let me know, I didn't feel like figuring out all the frontend stuff before getting your input.