fix #38766: bad input position after timesig change
fix warning reg. 'gridlayout6 is already in use'
Make the "View | Show Frames" command toggle-able

Currently the command cannot be toggled and using it hides the frames with no mean to show them back.
Merge pull request #1457 from mgavioli/view_show_frames_toggleable

Make the "View | Show Frames" command toggle-able
Merge pull request #1446 from Jojo-Schmitz/warning

fix warning reg. 'gridlayout6 is already in use'
Merge pull request #1449 from MarcSabatella/38766-timesig-inputpos

fix #38766: bad input position after timesig change
get Preferences -> shortcuts list back