fix #21205: don't show page number on first page

unless $P gets used instead of the default of $p, just like the default
setting for 1.x scores.
Also add $c and $C for copyright, with $c being a shortcut for
$:copyright: and $C showing it on first page only.
1.x compatibility for page number on first page
Move updated macro usage hint into a tooltip

generated in cpp rather than in the ui files.
Merge pull request #756 from Jojo-Schmitz/21207-text-macros

fix #21205: don't show page number on first page