In addition to significant internal differences in check_site_lib.lua (in
particular unifying error handling to a single place for the upcoming
multi-domain support), this changes the way fields are addressed in site
check scripts: rather than providing a string like 'next_node.ip6', the
path is passed as an array {'next_node', 'ip6'}.

Other changes in site check scripts:
* need_array and need_table now pass the full path to the sub fields to the
subcheck instead of the key and value
* Any check referring to a field inside a table implies that all higher
levels must be tables if they exist: a check for {'next_node', 'ip6'} adds
an implicit (optional) check for {'next_node'}, which allows to remove many
explicit checks for such tables

[Matthias schiffer: rebase, add a few more restrictions]

Fixes #1310

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

Some files have received some additional refactoring.

Fixes #1043

We also make use of the boolean support of simple-uci to make scripts
clearer.

Avoid commiting configs inbetween to decrease number of flash writes.

Fixes #714.

gluon-announced and gluon-announce are merged to gluon-respondd.

Moving the scripts to a common directory not only vastly simplifies the
zzz-gluon-upgrade script, but also allows to define an ordering of such
scripts across packages.

gluon-autoupdater: unconditionally perform an update 5 minutes after boot when the whole PRIORITY delay has passed

The probability field is removed, updates are performed once per night between
04:00 and 05:00.

All announce.d scripts have been moved to /lib/gluon/announce/announce.d
The script /lib/gluon/announce/announce.lua will collect all information
and output json.

Closes #31

This also fixes the type of a few fields which were strings instead of numbers.

On nodes with autoupdate disabled the cmdline parameter '-f' has no
effect. But using the autoupdater for manual updates is quite handy.