add posibility to use a unit schema other then the system schema to represent a quantity

src/Base/Quantity.cpp

@@ -213,6 +213,11 @@ QString Quantity::getUserString(double& factor, QString& unitString) const
     return Base::UnitsApi::schemaTranslate(*this, factor, unitString);
 }
 
+QString Quantity::getUserString(UnitsSchema* schema, double &factor, QString &unitString) const
+{
+    return schema->schemaTranslate(*this, factor, unitString);
+}
+
 /// true if it has a number without a unit
 bool Quantity::isDimensionless(void)const
 {

src/Base/Quantity.h

@@ -35,6 +35,7 @@
 #endif
 
 namespace Base {
+class UnitsSchema;
 
 struct BaseExport QuantityFormat {
     enum NumberOption {
@@ -143,12 +144,13 @@ public:
         _Format = f;
     }
     /// transfer to user preferred unit/potence
-    QString getUserString(double &factor, QString &unitString)const;
+    QString getUserString(double &factor, QString &unitString) const;
     QString getUserString(void) const { // to satisfy GCC
         double  dummy1;
         QString dummy2;
         return getUserString(dummy1,dummy2);
     }
+    QString getUserString(UnitsSchema* schema, double &factor, QString &unitString) const;
 
     static Quantity parse(const QString &string);
 

src/Base/UnitsApi.h

@@ -86,7 +86,6 @@ public:
 
     static double defaultFactor;
 
-protected:
     /// return an instance of the given enum value
     static UnitsSchemaPtr createSchema(UnitSystem s);