Fixes meshing over 802.11s.

Doing so caused broken validations, as different validators were affecting
each other.

Based-on-patch-by: Cyrus Fox <cyrus@lambdacore.de>

Based-on-patch-by: Cyrus Fox <cyrus@lambdacore.de>

The fastd_mesh_vpn site.conf section is renamed to mesh_vpn.fastd.

Updates batman-adv to 2017.0.1.

The ebtables rules were not adjusted when switching from macvlan to veth.

Switch sha512sum to sha256sum to match updated autoupdater.

The current autoupdater will only respect the last line for a given model
name, so we can add SHA256 checksums as long as they occur before the
corresponding SHA512 line.

This will ensure that gluon-site and gluon-autoupdater are rebuilt
correctly when GLUON_RELEASE or GLUON_BRANCH change.

The size of the factory images is limited to 4MB, which caused build
failures when many additional packages were included.

Rather than moving the device to ar71xx-tiny, we ignore the factory images
and just build the sysupgrade. This way, the whole flash is usable for
Gluon.

This means that installing Gluon on these devices will now require to flash
a plain LEDE image first, and then upgrading using the Gluon sysupgrade
image.

Fixes #1020

rpcd is not included in our images anymore since switching to gluon-web, so
we don't need to disable it anymore.

This makes the LAN port the PoE master, so the AirGateway can be used to
supply power to another node connected via mesh-on-LAN.

Fixes #608

We always want to prefer the unique node address for outgoing traffic. Note
that this doesn't have an effect with batman-adv, as usually br-client will
be the outgoing interface, so the unique address would be chosen anyways.