It's not supported by many clients, thus disable for now.

Exchange the signing key used by the CI/CD pipeline with a new key.

allow the SSID to change to the offline SSID once every 15 minutes

In non multi domain setups, vxlan is mandatory.

Release notes cites:
--- snip ---
In single domain setups, the new mesh.vxlan option is mandatory. It
should be set to true in new meshes; existing setups should set it to
false to retain compatibility with older versions of Gluon.
--- snap ---

It seems that we do have to wait until all Nodes are upgraded to
v2018.1, so we set it to false by now.

remove ibss

remove ibss mesh

+ update ffs-watchdog
+ update mesh ssid

The htmode option has been dropped, the channel width is now always set to 20MHz (https://github.com/freifunk-gluon/gluon/issues/487).