integrate Quantities into PropertyView and activate preferences again

src/Base/Quantity.cpp

@@ -27,6 +27,7 @@
 #include <cmath>
 #include "Quantity.h"
 #include "Exception.h"
+#include "UnitsApi.h"
 
 // suppress annoying warnings from generated source files
 #ifdef _MSC_VER
@@ -107,6 +108,11 @@ Quantity& Quantity::operator = (const Quantity &New)
     return *this;
 }
 
+double Quantity::getUserPrefered(QString &unitString)const
+{
+	return Base::UnitsApi::schemaPrefUnit(_Unit,unitString).getValue() * _Value;
+}
+
 // === Parser & Scanner stuff ===============================================
 
 // include the Scanner and the Parser for the Quantitys