I already have a "dumb import" (retag all files based on the filepath)
so there is no point in storing extra attributes when I am only going to
find them again during importing. Instead, we should only store the
information we need: filepath, score, and playcount.
Additionally, I now store the list of sources in the library backup.
We appear to already be locked when we get to the setter function. I
was getting deadlocked when trying to do anything. To fix this, I
made it so I can set images without needing the lock.
I can now import files from an Ocarina 4.1 library exported as xml.
Ocarina 4.2 keeps track of a list of sources, but 4.1 does not. For
importing to work properly, the library needs to be rescanned before
running the import. The import will set the playcount and score
attributes for each file.
