it's the same as HelpId in default implementation and extended with
'=?config=foo' string otherwise, depending on different configurations
the dialog/tabpage can have (e.g. different widgets hidden/shown)

Change-Id: I01312a5a88ef7ba784bca315b336420cdb63c8dc
Reviewed-on: https://gerrit.libreoffice.org/25455Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Katarina Behrens <Katarina.Behrens@cib.de>