Ups this won't work because exports are exported only to lower scripts
not back up so it can't be in separate file.

This implements support for new updater with relative URI and no model
variable.

This creates lists that can be included in to each other. This is done
by hack that original script calling one of these lists passes base URI
to access sources and that is later reused. This is how relative URI
should work in future but it is not completed now so we can overcome it
this way and have almost same support.

This also means that we no longer have to specify target branch for
lists because it no longer matters.

Fallback branch is for now dropped because we are not doing small build
at the moment. We should in future return to them but they will be
implemented differently then fallback branch is.

This also does some base list cleanup.

There has to be step between 3.x and 4.x version because of other
reasons than updater's incompatibility. That gives us possibility to
define new lowest supported version of updater-ng for 4.x releases.
Thanks to that we can remove some obsolete crap.

It is planned to bump minimal version of updater even higher as soon as
relevant updater's release is out.

Accept only lines that starts with 'src-git' not just contain that.

Make lists general. Board specific packages are handled by lua not m4
that meanst that we have same lists for all boards and specific sections
are ignored/skipped depending on model variable.

Script should still be run in OpenWRT directory but at the same time
because lists templates are no longer part of it can reach different
directory as a source.
Also removed hack for automatic generation of repositories and replaced
with better implementation in m4 it self.

Signed-off-by: Michal Hrusecky <Michal@Hrusecky.net>