Allow re-ripping a directory on disk.

[metaprime]

If, instead of a URL, you give a directory on the file system, load information about the rip from a log file saved in the directory, and use that to re-rip the content. This is one possible mechanism for more-easily incrementally updating content from a source that gets updates (user pages, etc.).

This also allows the scenario where ripped albums can be organized and moved elsewhere on the hard disk while still allowing re-ripping. The current re-rip functionality only allows albums to be re-ripped if they are in the original location. (Otherwise you get a duplicate of an album you'd already ripped and moved elsewhere.)

Related to #163