Fixes #373

15 is the default in batman-adv-legacy, the new default 30 in newer batman-adv
versions is too high in larger networks.

docs/site-example: explain how to re-enter configmode

Fixes #347

docs/autoupdater: depends on ipv6 reachable update-servers

fixes #365

This adds mesh_on_lan functionality.

A new optional site.conf option, mesh_on_lan, has been added. If set to
'true', all LAN ports will be used for meshing instead of being part of
the client bridge.

This will introduce a new nodeinfo object, network.mesh.bat0.interfaces,
containing any of the the following subordinated objects:

- wireless
- tunnel
- other

Each of these objects contains a (possibly empty) list of MAC addresses
(lowercase, colon-notation) corresponding to a interface of the given
class. Combined with a batman graph it is thus possible to mark
sub-graphs as "wireless" or "vpn".

The previously used object mesh_intefaces is superseded by this new
object structure and mesh_interfaces will be removed in a future Gluon
release.

Directly using libiwinfo is more reliable.

It would be nice to generalize this to work with multiple radios, maybe by
integrating it into the wifi-config module...

Fixes #219

This new package allows enabling or disabling the null method for the
fastd mesh VPN.

This new class allows visually pleasing lists of radio buttons/checkboxes/etc.
with long explanation texts.

All other titles are grey, the magenta-colored section titles inbetween look
weird.