Support refactoring of Unisons

[bwl21]

Request

we often have the problem that voices of a piece are combined as unsons. Separation int particular voices means

1. Duplicate the voice
   2 convert the unisons in either the first or the last note

Solution approach

Add a menu to editor pane which does this for a given selection:

• Replace by first note
• Replace by last note
• Swap first / last note
• Replace by second note
• Replace by last second note
• [ ]

\[([\^\_=]?[a-zA-Z][',]?)\s*([\^\_=]?[a-zA-Z][',]?\s*)*([\^\_=]?[a-zA-Z][',]?)+\]

yields either the first or the last note.

[bwl21]

there are more edit actions, so I reopen it