[Base]identify schemas which use multiple units

- allow querying a schema to determine if it uses multiple
  units for length (ex ft/in) or angles (ex DMS).

src/Base/UnitsSchema.h

@@ -65,6 +65,12 @@ public:
     virtual QString schemaTranslate(const Base::Quantity& quant, double &factor, QString &unitString)=0;
 
     QString toLocale(const Base::Quantity& quant, double factor, const QString& unitString) const;
+
+    //return true if this schema uses multiple units for length (ex. Ft/In)
+    virtual bool isMultiUnitLength() {return false;}
+
+    //return true if this schema uses multiple units for angles (ex. DMS)
+    virtual bool isMultiUnitAngle() {return false;}
 };