Add option to preserve all staves of multi-stave instrument
1. Open score
2. Hide Empty Staves.
Expected result: Unless the stave has been customised (i.e. only a treble clef), all staves in a multi-stave instrument should be retained.
Actual result: Only the staves featuring notes are retained, instrument names also disappear.
Using MuseScore 2.0 nightly build (4172) - Mac 10.4.11.