Add configurations for link-local networking for OPi images

[stephenjust]

When directly connected to a device, rather than through a switch, there is no DHCP server available. We can use link-local addresses to make the device automatically connect to client machines over link-local addressing.

On startup, the Orange Pi will attempt to connect via DHCP first, and only enable link-local if it cannot connect to a DHCP server after a few minutes.

[crschardt]

My concern with this link local config is how it will behave on a robot. If DHCP isn't available for some time at boot, it could drop to the link local config and then would become unreachable. This may be less of a concern with the new radio, but I don't know if this is a real risk and the code needs to be tested on a bot to find out. If the time to go link local is too long, then someone could plug it in to their computer and think that link local isn't working because they didn't wait long enough.

I had a version of a link local config that has both DHCP and link-local in the same connection but pulled it from the earlier commits because I'm not yet sure that it's safe. Here it is:

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    zz-all-en:
      renderer: NetworkManager
      match:
        name: "en*"
      dhcp4: true
      link-local: 
      - ipv4 
      networkmanager:
        passthrough:
          ipv4.dhcp-timeout: "2147483647"
          ipv4.link-local: "3"
          ipv6.method: "disabled"