Port away from most cases of Q_FOREACH to C++11 ranged for loop.

In order to avoid deep copies, Qt containers over which we iterate must be const
The remaining unported cases require qAsConst (Qt 5.7) or std::as_const (C++17)

This fixes CAL-385 #close

displaymanager: write processed DM list to globalstorage

This is disabled by default. To enable, provide a geoipUrl setting in
locale.conf.
Relies on the RequirementsChecker output, in the welcome module.

Since our default locale setting is **en_US** anyway, it makes more sense to default to New York.

Luks can only be done after you have ran **unpack**.

improve portage backend, so that properly removes reverse deps, whitout the need of HUGE package list in packages module configuration