Tor setup fixes

1. Add netcat dependency, which is used by the tor-get-orport script (used in the testsuite and by plinth).
2. Move Tor DNS port to 9053, so it doesn't interfere with dnsmasq. If we want to send all DNS requests over Tor, we can tell privoxy to use port 9053 as its upstream DNS server.
3. Configure Socks port only on interfaces with static IPs. This should avoid the issue where Tor cannot start due to invalid configuration if the DHCP-assigned address changes.
4. Fix typo in wifi setup script (installs firmware on Dreamplug if non-free repository is available).