refs #681, FSD UI at login screen

* plus completers for login GUI (ICAO, ...)
* some utility functions in related value object classed

src/blackmisc/aviation/airlineicaocode.h

@@ -180,6 +180,9 @@ namespace BlackMisc
             //! Valid designator?
             static bool isValidAirlineDesignator(const QString &airline);
 
+            //! Normalize string as airline designator
+            static QString normalizeDesignator(const QString candidate);
+
             //! From our DB JSON
             static CAirlineIcaoCode fromDatabaseJson(const QJsonObject &json, const QString &prefix = QString());