Release and Recording license improvements

[FibreTTP]

Currently, a release's license is only shown if all tracks on release share the same common license:

lms/src/libs/database/impl/objects/Release.cpp

Lines 658 to 660 in 5827594

	// various copyrights => no copyright
	if (copyrights.empty() || copyrights.size() > 1 || copyrights.front().empty())
	return std::nullopt;

lms/src/libs/database/impl/objects/Release.cpp

Lines 673 to 675 in 5827594

	// various copyright URLs => no copyright URL
	if (copyrights.empty() || copyrights.size() > 1 || copyrights.front().empty())
	return std::nullopt;

On Bandcamp, if an album has differing licenses depending on its tracks, it displays:

Some rights reserved. Please refer to individual track pages for license info.

I don't have an album like this ready to test with (I have one somewhere though), but I believe when tagging such an album with Picard (where on MB, the release does not have a CC URL, but one of the recordings do), it will only write the license and URL to the applicable track.

It would be nice if:

• On albums where there are multiple licenses, the album page mentions as such.
• The Track information modal shows what license the track is under.
• If there was some way to search for releases and recordings licensed under a certain license.