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

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.

Also fix error reporting.
Move guesswork to LocaleConfiguration + a total rewrite.
Locale is now a LocaleConfiguration, that converts to QMap.