by moving the declaration of ret to the top of get_fastd()

Fixes #1223

As the default package list is now handled using the 'packages' directive,
explicit wpad-mini removals in target definitions can be dropped.

This, together with a new try_config directive, will allow checking the
generic config and make it more flexible.

Adding the fact that GLUON_RELEASE is needed with 'make manifest'
if it is used with 'make'.

This fact was mentioned in the v2017.1 release notes but is not (clearly)
mentioned inside other parts of the documentation.

Signed-off-by: Chrissi^ <chris@tinyhost.de>

[Matthias Schiffer: minor rewording]

The older busybox-based wget erroneously accepted URLs without protocol.
Add validator to avoid building firmwares with broken autoupdates.

Adding hints that the next_node name should contain a dot to avoid (mobile) browsers interpreting "nextnode" as searchphrase. Also setting it to an fqdn helps when clients use static dns servers.

This device has built in wifi we should include it at least for experiments.

Some files have received some additional refactoring.

In particular, this affects users of gluon.util.iterate_radios.

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.