PMP & ePMP DNS

Let us configure more than two DNS servers. Three would work for me as we run three geographically diverse internal resolvers. Four might not be a bad idea. Technically, up to 13 should be allowed, but that's just overkill.

I'm talking about NAT mode LAN DHCP as well as remote management interfaces.

We do this for the PMP: 450, but not ePMP