fix user preferred

src/Base/QuantityPy.xml

@@ -34,7 +34,7 @@ Quantity(string) -- arbitrary mixture of numbers and chars defining a Quantity
         </UserDocu>
       </Documentation>
     </Methode>
-    <Methode Name="getUserPrefered">
+    <Methode Name="getUserPreferred">
       <Documentation>
         <UserDocu>
           returns a quantity with the translation factor and a string with the prevered unit