Enable MP4-AAC Cover ADD/Paste

Unlike most of the other CODEC, the AAC (Advance Audio Coding) Files
do not allow for Cover Art to be Added/Pasted etc.

The only way to add or paste a cover art graphic to AAC file(s) is to do a
multiple file update which include at least one MP3/WMA with the latter
being the last selected in the selection sequence.

That works, so the function works but yet it does allow it individually.