[localeq] Offer a Config setting to set location from region/zone

- already had methods for various kinds of broken-up data, but
  not one for plain "region/zone" strings; having this makes
  it easier for QML to report a zone.
- use the region/zone method from QML, so that clicking on the
  world map updates the actual TZ in Config.

src/modules/locale/Config.cpp

@@ -218,6 +218,15 @@ Config::setCurrentLocation()
     }
 }
 
+void Config::setCurrentLocation(const QString& regionzone)
+{
+    auto r = CalamaresUtils::GeoIP::splitTZString( regionzone );
+    if ( r.isValid() )
+    {
+        setCurrentLocation( r.first, r.second );
+    }
+}
+
 void
 Config::setCurrentLocation( const QString& regionName, const QString& zoneName )
 {