Singularize object creation form resource name. (#2684)

Currently the resource name on the object creation
form is showing in plural form.

This commit adds a `singular: true' parameter
to the display_resource_name method in the
object creation view to explicitly show the
resource name in singular form.

app/views/administrate/application/new.html.erb

@@ -18,7 +18,7 @@ to do the heavy lifting.
 <% content_for(:title) do %>
   <%= t(
     "administrate.actions.new_resource",
-    name: display_resource_name(page.resource_name).titleize
+    name: display_resource_name(page.resource_name, singular: true)
   ) %>
 <% end %>