config-mode, mesh-vpn: refactor key generation

Previously, the config-mode was responsible for generating the fastd
secret. This patch sets the default secret to "generate" causing a
secret to be generated on its first use (e.g. show_key or start).

This also changes the info page (in Expert Mode) to show "n/a" when the
public key is not yet available.

gluon-autoupdater: unconditionally perform an update 5 minutes after boot when the whole PRIORITY delay has passed

The probability field is removed, updates are performed once per night between
04:00 and 05:00.

The crontab file was opened in write mode but in the case where no monitor is defined it would leave an empty file.

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.

This allows to use cbi-field to format plain text instead of form fields.

This package provides a secondary dnsmasq instance on port 54 which resolves
everything over the WAN interface.

Also move it to gluon-mesh-batman-adv, as mesh_on_wan is the only feature that
needs a unique MAC address on the WAN interface.

gluon-batman-on-wan + gluon-luci-portconfig

The now empty gluon-firewall is removed.

This is a simple daemon that will respond to multicast UDP packets
containing the keyword "nodeinfo" with all the information we
currently distribute using alfred.

The daemon will listen on all mesh interface, that is the hard
interfaces batman-adv uses.

gluon-ath9k-workaround: Announce how often the workaround has been trigg...

This will make a node announce all MACs of its interfaces participating
in the batman-adv mesh. This enables other nodes to associate the
announced object with both the data reported by batadv-vis as well as a
simple list of neighbours as output by `iw dev $IFACE station dump`.

The support is still very limited (IPv6-only DNS on WAN doesn't work yet), and
we now need fastd running as root, but apart from that, is should work.