Allow Hidden Rest Default

At the inclusion of new measures, whole rests always appear. Each individual measure seems to need making each individual rest invisible. Two scores I'm working on now have no rests and 1 uses a proportional notation. A nice feature is the ability to make all rests invisible in the "staff/part properties" box. MuseScore already allows us to check boxes for show clef, show time signature, show barline, hide system barline, etc. Sometimes it good to have a "clean sheet of paper". It's tedious to manually make each rest invisible.