List all registred models (management command)

Exposed the ``watson.get_registered_models()`` function as management command for debugging purpose.

src/watson/management/commands/list_registered_models_watson.py

@@ -0,0 +1,16 @@
+"""Exposed the watson.get_registered_models() function as management command for debugging purpose. """
+
+from django.core.management.base import NoArgsCommand
+import watson
+
+class Command(NoArgsCommand):
+
+    help = "List all registed models by django-watson."
+    
+    def handle_noargs(self, **options):
+        """Runs the management command."""
+        self.stdout.write("The following models are registed for the django-watson seach engine:\n")
+        for mdl in watson.get_registered_models():
+          self.stdout.write("- %s\n" % mdl.__name__)
+        
+