v0.15.0

• added artist details pane
  • the pane shows artist biography from Last.fm if the API connection has been configured
  • the pane shows also the artist image if available in the user's library
• scan artist images from files named like "Artist Name.jpg" (or any other supported image file format)
  • the file name is case-sensitive
  • the image is provided via the route api/artist/{id}/cover
  • the image is available via the Ampache and Subsonic APIs
• support showing time-synced lyrics from file metadata (#657)
• tabbed layout for the track details pane (#657)
• sort tracks by the file names in the 'Folders' view (#770)
• open all external links to a new tab
• style all external links the same way as elsewhere in ownCloud and Nextcloud (underlined and postfixed with an arrow)
• proper handling for the keyboard play/pause button on Firefox (unlike Chrome and Edge, FF does not yet have a full media key support)
• fix app not working using URL with no trailing slash '/' (#765)
• fix Nextcloud notifications window empty layout being broken within the Music app on NC16+ (#772)
• fix the "empty album slots" layout problem reintroduced by Nextcloud 18 (#773)
• Ampache API improvements:
  • initial JSON API support (#768)
    • the API is not yet frozen by Ampache and the spec still has some inconsistencies
  • remove the <total_count> element from all results
    • this has been deprecated by Ampache, and none of the known clients seem to utilize it
    • removing the element already now simplified the implementation of the JSON API support
  • fix action tag returning the requested genre without track/album/artist counts
  • support filter and exact arguments also in the tags action (allows searching genre by name)
  • add <art> element to the artist results
• getID3 library updated to version 1.9.20
• AngularJS library updated to version 1.8.0
• drop support for ownCloud versions 8.2 and 9.x
• drop support for Nextcloud versions 9 - 12
• drop support for PHP 5.6
• drop support for Internet Explorer 9