Feature: Router-Mode w/ optional Captive-Portal

[Hades32]

We could add another mode: router / gateway mode.
In that mode the WiFi would have its own DHCP server, custom IP range and could (optionally) prevent access to the internal network on the Ethernet interface but just allow internet access. In that mode we should also NOT Route packets between clients.

Another extension to this feature could be a captive portal that would e.g. ask users to accept ToS before accessing the internet.

[luandro]

Any tips on how to add a Captive-Portal to this?