reduce ZET nameserver pain by clarifying Linux install for server vs. workstation

[qrkourier]

Workstation distros like Fedora and Ubuntu tend to have systemd-resolved pre-installed, which is required for ZET service to function with the default config.

Server distros like RedHat and Debian do not, so they must either install systemd-resolved or run-as root to enable manipulating /etc/resolv.conf, which does not perform as well as the default mode of operation.

Both RedHat and Debian distros' package managers have a concept of recommended or suggested packages, so we could include systemd-resolved as such a soft dependency and enhance the install script and instructions to do the right thing for server distros, which would be to not install systemd-resolved by default while making it convenient and obvious how to install it concurrently.