Add page 404 configuration menu entry to user group's Default permissions

[PMendesWebDev]

I don't really know if this is possible, but it would be great if we could manage the context menu item presence/display in the User Group's Default permission section.

That way the 404 page manager could be used by the groups instead of admin only

[NikRimington]

Interesting idea, it might be doable via a config setting as a first port of call. I'll see if I can look into it.