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

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.

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.

exec() is moved to gluon.util.

* change type of next_node.name
* create domain entry for each entry and add to dnsmasq configuration

[Matthias Schiffer: reword documentation]

Both gluon.sysconfig and libgluonutil already remove the trailing newline
if it exists. It's nicer to avoid files without a trailing newline, e.g.
for printing the file contents in a terminal.

Patch originally authored by @oleeander.

Fixes #424

Allows to remove some redundant UCI lookups.

Fixes #1322

The prefix is not used, and requesting it leads to odhcp6c log spam with
certain DHCPv6 servers.

Evaluating these rules before all the ICMPv6 rules improves wired mesh
throughput measurably.

On most devices, there is only a single LAN interface connected to all LAN
ports, so no bridge is necessary.

[Matthias Schiffer: rebase]

This should not convert JSON to a Lua table and back, as this loses the
distinction between arrays and objects, but as our site.conf is defined in
Lua anyways (for now), this can be fixed in a later revision.

[Matthias Schiffer: rename to gluon-show-site, rebase]

By basing the Lua gluon.site module on gluonutil_load_site_config(), the
config load implementation needs to changed only in a single place for
multi-domain support.

Fixes #1311

Fixes #1308

The 'auto' attribute still allows enabling the interface using ifup, which
is not intended when wired mesh is disabled.

As core defines basic rules for this zone, it makes sense to create it
there.

Based-on-patch-by: Christof Schulze <christof.schulze@gmx.net>

OUTPUT is always accepted, no need to allow ICMPv6 explicitly.

Wrap long lines.

 * gluon-core, gluon-client-bridge: introduce new firewall zone: local_client
 * gluon-core: put clients in local_client zone, introduce drop-zone,
   set dns-rules and zones
 * gluon-respondd: allow respondd on mesh
 * gluon-status-page-api: allow http input on mesh and client