Support for corrections in the Score Editor

[martha-thomae]

Add support for making corrections in the Score Editor (especially, adding dots) and for re-running the "scoring-up script" afterwards.

These edits in the score would correct errors present in the original images (scribal errors present in the manuscript), not errors made during user entry.

Being able to select a note and add a dot to it, or select a note and change its note-shape are some of the basic corrections needed.

[JRegimbal]

As of commit 3d2dbd42add63 dots can be added/removed from the score editor by clicking on a note and pressing .. Scoring-up will be run automatically after.

[JRegimbal]

It's now possible to also change the duration of a selected note using the same mapping as in the input editor and to adjust the pitch of a note by using the up and down arrow keys.

[JRegimbal]

Added the following features:

• Editing accidentals using the same controls as the input editor;
• Cloning a note by selecting it and pressing I; and
• Deleting a note by selecting it and pressing Backspace.

[karend27]

Nice - these all work well!