Support for scene name input from an index file or xattr

It would be nice to be able to take advantage of Bazarr's features for curated media libraries not currently relying on Radarr/Sonarr for renaming, such as Filebot or even manually renamed media.

Sub-Zero currently does a good job of providing options for some users in several ways:
Support for Filebot xattr, i.e. using `attr -qg net.filebot.filename <media file>` to retrieve the scene name automatically provided by Filebot on supported filesystems.
Support for Filebot external 'fake' xattr for filesystems that don't support xattr, optionally provided by Filebot in a file in the media directory folder of the form ".xattr/<new filename>/net.filebot.filename"
A very similar system offered by Sub-Zero using file_info index files, as described here: https://github.com/pannal/Sub-Zero.bundle/wiki/Refiners#file_info-index-files

Regardless if any/all of these options are implemented, it would then at least be possible to provide the scene name manually/scripted into postprocessing of media