MythMusic: fix the goom visualizer

* use the correct image format to convert the Goom buffer to a QImage
* re-enable the scale factors so you can reduce the cpu utililization
  Increasing the scale factors will reduce the amount of data to be processed
  by Goom but that will also make the image more blocky.
* increase the maximum scale factor to 4 (MythGoom allows 1, 2 or 4 to be used)

Fixes #11023.
MusicMetadata: make sure the various get*Id() functions return the actual ID

Under most circumstances getDirectoryId() will return -1 since by default we
don't fetch the proper ID until dumpToDatabase() is called. This was causing
dumping the AlbumArt to the database to fail because it requires a valid
directoryID.

This just makes sure getDirectoryId(), getArtistId(), getAlbumId and getGenreId
will fetch the proper ID if necessary rather than returning an invalid ID.
AlbumArtImages: add option to not load images from the database
Myth Protocol: add a MUSIC_FIND_ALBUMART command

This command will find the album art in the same directory as the track and
also look for any embedded album art in the tracks tag.

Format: MUSIC_FIND_ALBUMART <hostname> <songid> <update_database>
AlbumArtImages: add a scanForImages() function

This sends a MUSIC_FIND_ALBUMART command to the BE to find any directory and
embedded tag images for a track. The command is sent in its own thread so it
wont block the UI thread.
MusicImport: fix switching of the metadata editor to metadata only mode
MusicImport: update the importing of albumart to work with storage groups

Both directory and embedded images should now be imported properly.
MythMusic: start updating the edit metadata screen to work with storage groups
HLS: Don't allow duplicate streams to be created.

If an identical one exists we return the ID/details for that instead.
HandleMusicFindAlbumArt: only save the filename not the full path