Function globals canvas MFD_Generic PFD_Page setVisible

Makes a page visible.
It is the responsibility of the caller to manage the visibility of pages - i.e. to
make a page that is currenty visible not visible before making a new page visible,
however more than one page could be visible - but only one set of menu buttons can be active
so if two pages are visible (e.g. an overlay) then when the overlay removed it would be necessary
to call setVisible on the base page to ensure that the menus are setup