Adds webrtc.enable, webrtc.public_ip, webrtc.nat_1_to_1_ips, and
webrtc.udp_mux_port to the Core Data struct and registers each via
the existing vars system. Default is disabled; no behavior change
without explicit opt-in.
created_at represents the time when the configuration has been persisted to disk.
loaded_at represents the time when the configuration has actually been used.
If created_at is larger than loaded_at, then the Core needs a reload in order
to apply the latest configuration.
if created_at is lower than laoded_at, then the Core applied the latest
configuration.
The value of updated_at is irrelevant and shouldn't be used.
