Easily changeable DNS settings. #969

As any feature request, feel free to dismiss as not in the roadmap.

Is your feature request related to a problem? Please describe.
At home I have a DNS server that I control, so I let TC use it. But when I'm on a public WiFi, and sometimes with with my 4G carrier, the DHCP configured DNS refuses to resolves certain domains. In these cases I use some more trustworthy pubic DNS servers. But when I go back home, TC is not using the internal DNS, so I can't connect to local machines based on the local DNS.

Describe the solution you'd like
Ideally, DNS server settings based on the Internet connection/SSID, but this could be too much.

Second best, a dropdown that allows selecting from previous configured DNS server pairs, with an option for "none" (meaning use the DHCP ones), and an option to add a new pair.

Third option, a checkbox to disable arbitrary DNS servers, so I don't have to retype and delete them every time I switch from one mode to another.

The last two could include a different icon in the status bar so one could see if it's using an arbitrary DNS or not, but given it's so small maybe one would not notice anyway.

IMO.