factorize default images formats

app/controllers/media_controller.rb

app/helpers/application_helper.rb

app/services/importers/hash_to_person.rb

app/views/admin/application/featured_image/_edit.html.erb

...dmin/communication/blocks/components/image/_edit.html.erb

...in/communication/blocks/templates/image/_snippet.html.erb

.../communication/blocks/templates/persons/_snippet.html.erb

app/views/admin/communication/extranets/_form.html.erb

...admin/communication/websites/agenda/events/_list.html.erb

app/views/admin/education/schools/_form.html.erb

app/views/admin/layouts/themes/appstack/_top.html.erb

app/views/admin/layouts/themes/pure/_nav.html.erb

app/views/admin/layouts/themes/pure/_panel.html.erb

app/views/admin/university/organizations/_form.html.erb

app/views/admin/university/people/_form.html.erb

app/views/admin/users/_form.html.erb

app/views/devise/registrations/edit.html.erb

app/views/devise/registrations/new.html.erb

app/views/extranet/account/edit.html.erb

app/views/extranet/organizations/_form.html.erb