identities: add a get_preferred_language() method to Identity class

authentic/identities.py

@@ -322,6 +322,9 @@ class Identity(StorableObject):
         l.append('</PP>')
         return '\n'.join(l)
 
+    def get_preferred_language(self):
+        return None
+
     def get_display_name(self):
         if self.name:
             return self.name