courtesyAccidentals for MuseScore v3

Three plugins for MuseScore version 3.0.5 or higher to add or remove courtesy accidentals.

• addCourtesyAccidentals will add accidentals only in the following measure
• configCourtesyAccidentals can be configured via a dialog window
• removeCourtesyAccidentals will remove any accidental, that is not needed according to standard rules.

Please note that you need MuseScore v3.0.5 or higher for these plugins to work.

Because of limitations of the plugin framework, some of the custom options in the GUI version are still disabled for v3.