Update override field mapping tut

* Added reference to override section of inheritance-mapping.rst
* Added link to yaml/xml examples in override-field-association-mappings-in-subclasses.rst

docs/en/reference/inheritance-mapping.rst

@@ -260,6 +260,7 @@ or auto-increment details). Furthermore each child table has to
 have a foreign key pointing from the id column to the root table id
 column and cascading on delete.
 
+.. _inheritence_mapping_overrides:
 
 Overrides
 ---------

docs/en/tutorials/override-field-association-mappings-in-subclasses.rst

@@ -87,4 +87,4 @@ The case for just extending a class would be just the same but:
         // ...
     }
 
-Overriding is also supported via XML and YAML.
+Overriding is also supported via XML and YAML (:ref:`examples <inheritence_mapping_overrides>`).