v2.3.3

1. For Opus files, use R128_TRACK_GAIN and R128_ALBUM_GAIN to store replaygain values.
2. Remove user-agent checking when serving local files, this is easily fake-able and breaks playback to forked-daap (and mopidy?)
3. Add '.opus' to list of recognised extensions for local files.
4. Initialise network proxy factory when starting.
5. If artist, album, and title are empty in replaygain dialog, then show filename in title column.
6. Opus does not use replaygain peak tags, so do not write.
7. Use same 'album key' for all discs in an album, so that playqueue groups them together, and shuffle by albums keeps them together.
8. Remove confirmation dialog when saving replaygain tags.
9. Fix saving 'Descending' order for smart playlists.
10. When getting 'basic' title of song, also remove any 'prod. XXX', etc. values.
11. Allow .jpeg as extension from cover dialog.
12. Fix QMediaPlayer stuck with network streams - thanks to theirix
13. Always show volume control.
14. Fix 'Show Current Song Information' (i) toolbar button showing when interface is collpased and resized.
15. When expand intrface, don't shrink width. Conversely, when collapsing don't expand width.
16. In grouped style playqueue, only show album duration if there is more than one track from the album.
17. Don't try to reduce brackets when showing album name and year.
18. Add option to sort smart playlists by title.
19. Change toolbar colours if palette changes.
20. Add another qt5ct palette work-around.
21. Don't stop library scan just because of failure in 1 directory.
22. Handle empty VolumeIdentifier in MTP devices.
23. Add more actions to search page results.
24. For MPD>=21, use its albumart protocol to fetch covers.
25. When copying tracks to a device, only update cache if configured to do so.
26. Fix MusicBrainz disc ID calculation.
27. When loading URLs via commandline use AppendAndPlay.
28. MPRIS seeks command specifies an offset from current position.

NOTE There are no windows or mac binaries, as I will no longer be creating these.