[AFV] Ref T739, unified callsign functions in CAfvClient

* improved CallsignSet from QStringList
* renamed the functions which just return a string
* added functions for CCallsignSet

src/blackmisc/aviation/callsignset.h

@@ -35,7 +35,7 @@ namespace BlackMisc
             CCallsignSet();
 
             //! By string list
-            CCallsignSet(const QStringList &callsigns);
+            CCallsignSet(const QStringList &callsigns, CCallsign::TypeHint typeHint = CCallsign::NoHint);
 
             //! Construct from single callsign
             CCallsignSet(const CCallsign &callsign);