The .ui files are all GPL-3.0-or-later style, but it's
slightly difficult to keep licensing information in them:
it's XML, so an XML comment might work, but there's no
guarantee that safe/load will preserve them.
Put the SPDX tags in the <author> tag, so that it's visible
in Qt Designer.
Untangle the shortcuts; Create and Cancel had an overlap.
Skip 'r' (Revert all changes) and 'e' (Edit) and settle on
'a' (which might also mean "Add").
FIXES#977
