Fix #19472

Implements [Left] / [Right] not only from notes/chord-rests but from any element whose parent is a note, a chord-rest or a segment
For elements attached to segments, move to the chord/rest in element track, if it exists
Stops continuous reformatting of float data entered in inspector widgets
TAB formatting re-aligned with changes on semantics for chord and stem function computing stem data.
Update README.md
add some checks for corrupted input files
Stops continuous reformatting of float data entered in EditTools widgets.
Merge pull request #180 from mgavioli/Fix_#19611_#19709_tab_stem_too_long

Fix #19611 and #19709 - TAB stems too long
fix stem layout (beam + tweaked note head)
fix importing spanner from 1.2
Corrects vertical alignment for stemless notes (semibreves and breves).
First commit too simplistic and didn't work for ledger lines.

Error was in determining stem X pos. Improved.
Merge pull request #181 from mgavioli/Fix_#19455_entering_floats_in_inspector

#19455 - Entering float numbers in inspector
Merge pull request #183 from mgavioli/Fix_#19455_entering_floats_in_editttols

#19455 Entering float numbers in EditTools
Merge pull request #184 from mgavioli/Fix_#19809_semibreve_and_breve_vert_misalignment

Fix #19809 Semibreve and breve vertical misalignment
Merge pull request #156 from mgavioli/Fix_#19472

Fix #19472: [Left]/[Right] from more element types
create clef for all system - bugfix
fix typo and infinite loop in selectedNote()
Merge pull request #186 from AntonioBL/firstsystem

Fix #19852 : "Create clef for all systems" not working properly when unchecked
enhance 1.2 symbol import