Right click context menu in note entry mode

I've placed two pull request which implement a right click menu in note entry mode and shadow notes which represent the set duration while in note entry mode. Marc suggested to introduce these topics for dicussion, which I'd like to do with this post.

1. A new menu entry in the right click context menu enables the user to switch to note entry mode



2. A right click in note entry mode opens a context toolbar which allows the user to change duration, dots, accidentials, voices etc. on the note entry spot. The user can also exit the note entry mode, do some editing and reenter note entry mode by using the new menu entry introduced  in 1.



3. If the user changes the duration of a note in note entry mode, the shadow note now shows the right note and not just a filled or empty note head.



Cheers
19joho66