Improvement to the Score/Staff/Voice Editors

[Richard Shann]

If you have a lot of customization then the Score editor can be quite
daunting - looking down all the properties trying to find the one you
want to look at is tiresome.
To alleviate this I've now put a selector at the top of the page - all
the properties are listed and you can choose just one or two to
actually show below. (For backward compatibility all are showing at
first, but there is an Invert Selection button to hide them).

Richard