Build requires Python 2 and libssl-dev

When rebooting the node in config mode, currently the fastd key is
forcefully displayed in a fixed format. This is confusing in communities
where fastd accepts all keys and no key submission is needed.
Furthermore, some communities might want to personalize the display of
the key (see #387).

This patch moves the displaying <div> from the package's lua file to the
translation files of the sample site configuration and mentiones the
change in the release notes.

Split basic radio configuration from gluon-mesh-batman-adv as this will
be required for virtually any wireless mesh protocol.

This package takes care of setting:

  - wireless channel,
  - htmode and
  - regulatory domain

gluon-mesh-batman-adv-core depends on this package.

Documentation for packages should be placed in docs/packages/
and be added to docs/index.rst.

This is a site.conf-breaking change in regard to the wireless config.
Make sure to read http://gluon.readthedocs.org/en/latest/user/site.html
and update your site.conf accordingly!

Support for 802.11s mesh interfaces has been added. Gluon now supports
three interface types: ap, ibss and mesh. All of them are now optional
and may be configured independently in site.conf.

A sample site.conf may look like this:

    wifi24 = {
            channel = 1,
            htmode = 'HT40+',
            ap = {
                    ssid = 'luebeck.freifunk.net',
            },
            ibss = {
                    ssid = '02:d1:11:37:fc:38',
                    bssid = '02:d1:11:37:fc:38',
                    mcast_rate = 12000,
            },
            mesh = {
                    id = 'ffhl-mesh',
                    mcast_rate = 12000,
            },
    },

see: http://gluon.readthedocs.org/en/latest/releases/v2014.3.html



Signed-off-by: Alexander Dahl <alex@netz39.de>

The file targets/$GLUON_TARGET/config becomes optional, as many targets
only used it to set the board and subtarget.

Also fix targets without subtarget.

Fixes #373

Fixes #347

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.