- Fix #279071: "Don't Break" element creates hole at end of system
- Allow more than two measures to be grouped
- Allow adding/toggling NOBREAK by clicking palette
- Rename to "Group Measures"
- Adjust placement of break symbols
Co-authored-by: MarcSabatella <marc@outsideshore.com>

- Public before private
- Members prefixed with "m_"

…btypes 1/2/4

- Draw with font symbols instead of QPainterPath
- Automatically group measures and delete contents when adding MeasureRepeat
- Bring measure.h and measure.cpp in line with new code guidelines
- Hide rests by making measures (per MStaff) aware if they are part of measure repeat group
- Keep measures and element in sync at all times by handling (preventing/warning/special-casing) many user actions
- Add style options for numbering consecutive one-measure repeats

MMRests:
- Add vtests for old-style (all fonts), h-bar thickness and margin (Bravura)

MeasureRepeats:
- Add script tests for adding, cutting/copying with partial group selected, pasting into group, repeating selection from before group, executing split/join/insert/delete measure commands, adding repeat barlines, and adding time signature
- Add mtests for parts, MIDI, and MusicXML import/export
- Add vtests
- Update ref files