The new gluon.site lua library will eventually replace gluon.site_config
(which is hereby deprecated, but will continue to be supported for a
while).

The new gluon.site library will wrap all values to allow traversing
non-existing tables without errors.

    site = require 'gluon.site'
    c = site.a.b.c -- doesn't fail even if a or a.b don't exist

The wrapped values must be unwrapped using call syntax:

    site_name = site.site_name()

Using the call syntax on a non-existing value will return nil. An
alternative default value may be passed instead:

    mac = site.next_node.mac('16:41:95:40:f7:dc')

Fixes #1021

simple-uci will now delete an option when nil is passed.

simple-uci will now delete an option when nil is passed.

simple-uci will now delete an option when nil is passed.

simple-uci will now delete an option when nil is passed.

uci:set_list() will delete the list when nil is passed, so there is no need
to differentiate between the cases.

The generic upgrade script is moved to run after the more specific scripts.
In addition, the script will now remove the configuration sections of
uninstalled VPN packages, so both positive and negative changes of the
default enable state can be migrated correctly.

Based-on-patch-by: Cyrus Fox <cyrus@lambdacore.de>
Fixes: #1187

This reverts commit 819758f4.

A proper fix is now available, therefore reverting this workaround.

Updates batman-adv and alfred to 2017.2 and adds the batman-adv TT-sync
fix.

Fixes #1183

When a Gluon node is used to connect to an uplink router/DHCP server (for
example in deployments without VPN tunnels), the gw_mode must be set to
server; this should be preserved on upgrades.

Fixes #1196

[Matthias Schiffer: move to proto_gluon_bat0_setup() and default to BATMAN_IV]

Improve error handling a bit, and fix upgrade for some (unsupported or
broken) targets.

.SHELLSTATUS was not available before Make 4.2.

gluon-mesh-babel is not merged yet, and once it is, this would lead to a
circular dependency.

To reduce the number of packages that need to be listed in
GLUON_SITE_PACKAGES, this adds a new variable GLUON_FEATURES. Sets of
packages are enabled automatically based on the combination of listed
feature flags.

Site-specified package feeds can provide their own feature flag
definitions.

These packages don't work or don't make sense without batman-adv.

Update "scripts: metadata: always resolve dependencies through provides
list" to new version.

As PROVIDES can be used to replace real packages now, we don't need the
virtual packages as workaround anymore. This also means that the providing
packages don't need to be added to site.mk explicitly anymore when the
default provider is used.

Allow to use PROVIDES to replace existing packages.