fix sort + preserve tracknr and discnr from metadata about stretto HOT 1 CLOSED

Musicmetadata (the library we use for most of the scanning) finds those attributes (see here) so we might want to add it to the patch script to rescan all the known library but only update that data (and to add it to the normal scanning by default).

Also with regards to the sorting, perhaps when the data is being loaded on the client we make that the primary sort value after the artist and album so that when we sort by album or artist they are in the order we want.

I guess I have never noticed this because I don't really pay attention to the order of songs in albums (I normally have things on shuffle anyway).

I'll implement this sometime in the long run (I'll leave the issue open) and if you want it done faster you can feel free to submit me a PR.

from stretto.