#33546: export key-accidental
#33546: move convertAccidental() to musicxmlsupport.cpp
#33546: import microtonal accidentals in non traditional key signatures
possibility to close startcenter from webview, open mscz from start center
Merge pull request #1569 from lvinken/33546-non-standard-keysig-musicxml

33546 non standard keysig musicxml