Add ability to explicitly break links between linked staves/parts
GIT commit: 6c5b016
Right now, elements and edits are either linked or not; users has no choice in the matter. If MuseScore fails to link something you want linked, it's easy enough to workaround - just make the change manually in both place. But iof MuseScore links something you don't want linked, it is not so easy - you would have to resort to creating duplicate items and hiding them. An explicit command to break a link would be helpful.