Provide an edit button for static mapped entries

As suggested in forum https://forum.pfsense.org/index.php?topic=82883.msg0#new
Instead of a non-functioning red plus icon, show an edit icon for static mapped entries, and take the user to services_dhcp_edit page if it is clicked. IMHO this makes it much easier to correct things that are noticed when viewing the Status, DHCP Leases display.
I had also thought this would be handy but never got around to looking at it - so now here it is if it seems useful.
I have tested a few editing combinations, and even the Cancel button on services_dhcp_edit happily takes the user back to status_dhcp_leases.