Updates

• Made some UI states persistent across sessions #484
• Added support for record labels #502
• Added compilation tag support #520
• More permissive grouping of multi disc albums (each disc can now be split on sub directories) when musicbrainz ids are not set #481
• Improved the artist display name string reconstruction to match more case #491
• Apply all custom separators, not only the first one found #518
• Now buildable on macOS
• Subsonic API: report the cover of the release if no embedded cover is found for the track #519