1. Translation updates.
2. Remove any leading slash from xxx_svg.png paths.
3. Add custom actions to context menus.
4. Allow adding custom actions to album track, queue, playlist, and playlist tracks' context menus (use "album-track", "queue-track", "playlist", or "playlist-track" as section in JSON file).
5. Allow replacing "$IMAGE" with item's image URL in custom actions.
6. Fix "lmscommand" custom actions.
7. Fix RadioNet icon mapping.