AutoDownload.py: just give it a path and have missing subtitles download...

yep, i'm that lazy. just call this script with a path, it will find all movie files without a sub/srt file, and will call OpenSubtitlesDownload on them. 

it's a horrible quick'n'dirty hack, but if you think someone might find it useful, pull away!

hardcoded MAX_MOVIES=50 not to flood OpenSubtitles with too many requests.

possible enhancements:
* maybe there are more subtitle extensions than srt and sub? or does OpenSubtitles only ever return srt files? i have no idea
* argparse the maximum movie count
* support other languages than English
* share the movie extension array with the main script (currently copy-pasted. told ya i'm lazy)