default "search by movie hash" is too narrow

[milahu]

by default, subdl uses "search by movie hash" to find subtitles

problem: when i have a 720p release, it has a different movie hash than a 1080p release, so subdl finds less subtitles than expected

potential problem with "search by filename": abbreviated filenames like asdf.mp4. maybe change the default to "search by filename", and add a hybrid mode "search by filename and movie hash"

continue #31