7088: provide a config option to suppress the warning about missing "sdn"


git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@23206 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
7089: webcal mistreats non-gregorian event dates

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@23208 4ae1f11a-8b86-4847-b8af-ab372f36d1fd