gluon-config-mode-contact-info: provide enhancements for german, english and french translation to comply with DSGVO (#1394)

* do not allow to obligatorily require contact information
* add remark that the data is provided voluntarily
* mention how to delete the data
* be very clear about the fact that the data being entered is public and
  can be downloaded and processed by anyone.

This commit adds the ability to show information about the platform on
config-mode reboot.

This commit adds information about:
- how cpu time is spent since boot in jiffies (1/100*sek) (cpu)
    - the value is summed for all cores, so in 10 seconds the
      summed values will increase by 4000, if the cpu has
      4 cores
- context switches since boot (ctxt)
- interrupt counters since boot (intr, softirq)
- forks since boot (processes)

    { "stat": {
       "cpu": {
         "user": 219403,
         "nice": 1714,
         "system": 75159,
         "idle": 2727739,
         "iowait": 2943,
         "irq": 0,
         "softirq": 571
       },
       "intr": 8426340,
       "ctxt": 50992590,
       "processes": 10549,
       "softirq": 5161884
    } }

In multidomain setups, VXLAN is enabled by default, but can be disabled in
domain configs using the mesh/vxlan option. In single domain setups, the
mesh/vxlan option is mandatory.

The UCI option for legacy mode is removed.

Fixes #1364

Fixes: 8e5abf02 ("treewide: switch to ebtables-tiny")

The local_node ifstatus must be checked for local-node, not client. While
we're at it, also clean up the syntax a bit.

batman-adv-specific parts are moved to a new package
gluon-status-page-mesh-batman-adv.

gluon-core, gluon-l3roamd: introduce script gluon-list-mesh-interfaces that lists all currently active mesh interfaces

gluon-status-page: reduce usage of absolute paths in cgi-bin scripts neighbours-nodeinfo and stations

The field is unused.

dnsmasq's caching is severly broken and does not handle all answer records
equally. In particular, its cached answers are missing DNSKEY and DS
records, breaking DNSSEC validation on clients.

Remove the cache for now. It may return if dnsmasq is fixed or we switch to
a different resolver.

The script cleaned up an old setting that was removed in 2014.

net.ipv6.conf.br-client.forwarding is moved from gluon-client-bridge to
gluon-mesh-batman-adv, as the setting is not useful with non-bridged
protocols.

With the batman-adv multicast support compiled back in again we end up
with multicast addresses in the batman-adv translation table.

Currently we wrongly interpret multicast addresses returned by TT as a
unique host, too, which adds them with a source address filter to
ebtables as well. However, the source address of an ethernet frames is
never supposed to be a multicat one.

This leads to unnecessary entries in ebtables. Fixing this by ignoring
those MAC addreses returned by TT which have the multicast bit set.

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

Signed-off-by: Jan-Tarek Butt <tarek@ring0.de>

* Use correct width
* Don't display focus outline (Webkit)
* Don't let option elements inherit error colors (Webkit)

Some HTTP endpoints were writing annoying "broken pipe" messages to stderr.

This setting allows to enforce manually setting a hostname.

In the initial configuration, the hostname field is now left empty; when
setting the hostname is not enforced, the default hostname is shown as the
field placeholder.

Fixes #1139

Also add documentation about config mode settings.

Our VXLAN setup was changed to accept VXLAN packets without checksum almost
2 months ago, so we can disable sending the checksums now as well. Slightly
improves performance.