Add has_subclasses checks for iplugins (prevent for loading parent class)

iplugin.py

@@ -79,13 +79,19 @@ def preloadPlugins(plugins, iwla):
                 classes = [c for _,c in inspect.getmembers(mod)\
                                if inspect.isclass(c) and \
                                issubclass(c, IPlugin) and \
-                               c.__name__ != 'IPlugin'
+                               c.__name__ != 'IPlugin' and \
+                               not c.__subclasses__()
                            ]
 
                 if not classes:
                     logger.warning('No plugin defined in %s' % (plugin_path))
                     continue
 
+                if len(classes) > 1:
+                    logger.warning('More than one class found in %s, loading may fail. Selecting %s' % (plugin_path, classes[0]))
+                    print classes
+                    continue
+
                 plugin = classes[0](iwla)
                 plugin_name = plugin.__class__.__name__