Network autoconfiguration

[sfalexrog]

As of now, wireless network reconfiguration requires multiple steps:

• change wpa_supplicantconfiguration;
• change /etc/dhcpcd.conf;
• enable/disable dnsmasq.service (depending on AP/station config);
• restart dhcpcd.service (or the whole RPi).

This is tedious, and each step may be performed erroneously, resulting in a system that won't bring up the network.

Obviously, we should and can do better than that.

This P/R proposes adding a dhcpcd hook and changing dhcpcd config to use static IP as a fallback configuration. With this P/R, network reconfiguration is now a two-step process:

• change wpa_supplicant configuration;
• restart the whole RPi (not sure about just dhcpcd.service).

P/R progress:

• [x] default config changes;
• [ ] test image with this P/R applied;
• [ ] documentation changes;