keep macfilter and maclist config after fw-update

This also takes us past the OpenWrt 15.05 final release.

Build requires Python 2 and libssl-dev

docs: Suggest MTU 1280 to circumvent Kabel Deutschland problems

docs: Suggest peer limit 1 instead of 2

CONTRIBUTING.md: Typo "everybode"

add: info for 802.11s interface (mac)

additional information for commit 2a93c580

LuCI's authentication won't work without rpcd, but we aren't using the
authentication anyways. Users who need it can just install rpcd explicitly.

Fixes #452

Now that the status page api has been rewritten in C CPU load and memory
usage is much lower. Also, nodes with both ibss and 11s mesh and dual
band wifi may require up to 9 connections for a single client, thus the
previous limit of 12 seemed a little low.

This will make it easier to replace the API with C programs.

Convert option ifname in br-client to use a list instead. This
simplifies adding and remove interfaces:

uci:add_to_set("network", "client", "ifname", "eth0")
uci:remove_from_set("network", "client", "ifname", "eth0")

An option ifname will be automatically converted to a list when
performing an upgrade.

Packages affected: gluon-mesh-batman-adv-core, gluon-luci-portconfig

Don't fork batctl from announce scripts

This reverts commit 91b3c1d3.

This reverts commit 6da1677d.

RFC: Add contribution guidelines

Add patch "luci-lib-jsonc: Fix memory leak in stringify"