Fix issue #24468 - Tremolo exporting to parts
Completing tremolo export to part changes,
http://musescore.org/en/node/24468, adding functionality for
adding/deleting after part creation.
Merge branch '20082-PartExportFailure' of github.com:MarkRS-UK/MuseScore into MarkRS-UK-20082-PartExportFailure
fix test for tremolo in GP5 import
Merge branch 'MarkRS-UK-20082-PartExportFailure'
fix #25703: wrong clef for 1.3 scores with odd clef change
staff type edit updates
enabling more metaTags
fixing typos found along the way
fixing the regression test files in mtest
improving content for platform tag
removing "Platform" tag from all mscx files

as it is case sensitive and really should be "platform" and as such
would be ignored during tests
rebase and adjust to new regression test files