fix #28336: Sending 'program change' message to JACK MIDI Out
Proper implementation of stopNotes() and initInstruments() for the calls from UI and RT threads
fix #31471: system text edits not linked
fix #31496: lyrics not propagated to existing parts
fix #31301: misaligned half notes
update & add vtests
Simple key signature detection algorithm
fix #31711: chord symbols & mmrests
fix #31436: segno et al do not display in mmrest
fix #30266: Some button labels are not translated

Fixed by replacing QDialogBottonBox by QPlatformTheme, which seems what
Qt 5.2 (?) and 5.3 (!) needs as the context, to load the right
translations for these button labels.

Also some more cosmetic fixes for the German translation
Fix #31176 - Appearing and disappearing courtesy clef

When courtesy clefs are turned off, some sequences of steps involving clef changes across system breaks result in spurious courtesy clefs being shown. Also, occasionally, the layout oscillates between showing / hiding courtesy clefs and/or fitting its measure in the same system or the next system. See http://musescore.org/en/node/31176 for details and examples.
Merge pull request #1251 from trig-ger/midi_key

Simple key signature detection algorithm for MIDI import
Merge pull request #1239 from MarcSabatella/31471-system-text-link

fix #31471: system text edits not linked
Merge pull request #1254 from MarcSabatella/31301-half-alignment

fix #31301: alignment of half notes
Merge pull request #1268 from MarcSabatella/31711-chord-mmrest

fix #31711: chord symbols & mmrests
Merge pull request #1145 from Igevorse/jack-transport

fix #28336: Sending 'program change' message to JACK MIDI Out
Merge pull request #1269 from MarcSabatella/31436-segno-mmrest

fix #31436: segno et al do not display in mmrest
fix selection detection of colornotes plugin
fix warning, unused variable
fix #32166