Tweak default "model title" logic for master view

i.e. if view class doesn't declare one

tailbone/views/master.py

@@ -1780,7 +1780,14 @@ class MasterView(View):
         """
         if hasattr(cls, 'model_title'):
             return cls.model_title
-        return cls.get_model_class().get_model_title()
+
+        # model class itself may provide title
+        model_class = cls.get_model_class()
+        if hasattr(model_class, 'get_model_title'):
+            return model_class.get_model_title()
+
+        # otherwise just use model class name
+        return model_class.__name__
 
     @classmethod
     def get_model_title_plural(cls):