This adds a `node_id` to announce.d. `node_id` is an hex-number uniquely
identifying a particular node. On nodes having a
primary MAC this MAC address will be used as `node_id` (sans the
colons). The value is opaque. It must not be converted back into
a MAC address.
`node_id` should be sent in all alfred and announced packets to
ensure clients can link the data to a particular node.
All announce.d scripts have been moved to /lib/gluon/announce/announce.d
The script /lib/gluon/announce/announce.lua will collect all information
and output json.
