mapsettings - activate OGC standards if relevant
mapsettings - Activate checkboxes on OGC std tab
mapsettings - OGC tab checkboxes

Some cosmetic changes + removing debug trace + blacklisting some extra
options in the model.
mapsettings - adding validators for extent
mainwindow / app - CLI extra argument

Gives the possibility to call the binary with an extra argument to
preload a mapfile.