Fix contextpopup

contextpopup was broken on desktop because of https://github.com/geoadmin/mf-geoadmin3/commit/b0831a4e71d057d911b63f77b610f9817f34d803

I revert this fix and apply the old behavior : 
 - mobile version -> long touch
 - desktop version -> contextmenu event if exist otherwise long touch

I made this because IE 11 on mobile has an event contextmenu but not triggered on long touch like on Surface