refs #413, #416 Implemented base_type fallthrough in Mixin::Index so it can be used by more classes.

(cherry picked from commit d97775a232b007061cbfa85b451b0be569127696)

src/blackmisc/pq/physicalquantity.cpp

@@ -371,7 +371,7 @@ namespace BlackMisc
             case IndexValueRounded6DigitsWithUnit:
                 return CVariant::from(this->valueRoundedWithUnit(6));
             default:
-                return Mixin::Index<CPhysicalQuantity<MU, PQ>>::propertyByIndex(index);
+                return Mixin::Index<PQ>::propertyByIndex(index);
             }
         }
 
@@ -400,7 +400,7 @@ namespace BlackMisc
                 this->parseFromString(variant.toQString());
                 break;
             default:
-                Mixin::Index<CPhysicalQuantity<MU, PQ>>::setPropertyByIndex(variant, index);
+                Mixin::Index<PQ>::setPropertyByIndex(variant, index);
                 break;
             }
         }

src/blackmisc/pq/physicalquantity.h

@@ -45,7 +45,7 @@ namespace BlackMisc
         template <class MU, class PQ> class CPhysicalQuantity :
             public Mixin::DBusOperators<CPhysicalQuantity<MU, PQ>>,
             public Mixin::JsonOperators<CPhysicalQuantity<MU, PQ>>,
-            public Mixin::Index<CPhysicalQuantity<MU, PQ>>,
+            public Mixin::Index<PQ>,
             public Mixin::MetaTypeAndQList<PQ>,
             public Mixin::String<PQ>,
             public Mixin::Icon<CPhysicalQuantity<MU, PQ>>