fix #19904: Import of 1.2 TextStyles for titles

Add compatibility with TextStyles for 1.2 titles:
Change the 1.2 TextStyle "Poet" to "Lyricist" for 2.0.
Remove the zeroing of Rxoff and Ryoff, which causes title, subtitle,
composer and lyricist to be misplaced.
fix crash in MusicXML with tie
hide additional media behind experimental flag
fix multiple bugs in fret diagram handling
hide fret diagram frame behind experimental flag
fix crash when pressing Join Score and no album
fix tremolo bounding box in palette
fix #11118: Join Scores causes crash
read only spinboxes in debugger dialog
fix #19612
Merge pull request #202 from lvinken/musicxml-fixes

fix #19612
Add a test case score
Update the test harness to include textstyles
Merge pull request #198 from softins/1.2-titles-import

fix #19904: Import of 1.2 TextStyles for titles
add creation date as a meta tag in mscx file
small build update
fix text palette crash
layout fixes for edit styled text
add -t command line to create test case files, add test documentation