Fixes #1130

Reverts d5829d87 ("gluon-mesh-batman-adv-core: disable bridge port
learning on bat0").

Fixes #1121

LEDE recently disabled multicast snooping by default:

https://git.lede-project.org/?p=project/netifd.git;a=commitdiff;h=52541140f8138e31958cdc3d7e42a4029fa6bbc9



Reenable it for Gluon as there have been no confirmed issues for
LEDE and no negative reports concerning Gluon v2016.2.x so far.

Closes #1025.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

LEDE recently disabled multicast snooping by default:

https://git.lede-project.org/?p=project/netifd.git;a=commitdiff;h=52541140f8138e31958cdc3d7e42a4029fa6bbc9



Reenable it for Gluon as there have been no confirmed issues for
LEDE and no negative reports concerning Gluon v2016.2.x so far.

Closes #1025.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

We now create bat0 and primary0 independently of the lower mesh interfaces,
making the whole setup a lot more robust. In particular:

- we can't accidentially destroy primary0 because of concurrent setup and
  teardown runs of different interfaces
- bat0 will always exist, even when no mesh interfaces are up (e.g. no link
  on wired mesh)
- interfaces going down and up again will never tear down the whole of
  batman-adv
- we can enable and disable bat0 independently of the lower interface
  states

For simplicity, we don't use different MTUs for compat 14 and 15 anymore,
there's no harm in using 1532 for batman-adv-legacy as well.

In addition, transitive and fixed_mtu now default to 0 instead of an empty string.

gluon-core: gluon.util: pass UCI cursor as argument to iterate_radios() instead of using local context

batman-adv 2017.0 doesn't need (or support) no_rebroadcast anymore. Don't
fail when the file doesn't exist.

VPN daemons were always disabled

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.

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

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.

This was introduced in ffhh-packages at https://github.com/freifunkhamburg/ffhh-packages/tree/master/gluon-config-mode-reboot-ffhh

Make use of our new _translate() function.

_translate() will return nil when no match is found.