[Scales] Add "root to root" mode

[damassi]

Select one root note and the tool shows all other available root notes that are not the same pitch. User selects one of those other roots and the tool fills in the selected scale in between the two roots.

Idea courtesy of http://mikehadlow.blogspot.com/2018/09/what-i-learned-creating-guitar.html?showComment=1537557952068#c1621655626219790279