Add web based python shell to Melange. It is accessible via http://host/admin/shell url and requires developer rights. Shell project is part of google-app-engine-samples. This commit moves django configuration from main.py to separate gae_django.py module. Shell project has been modified in order to work correctly with django 1.0+. Build script has been updated and includes shell folder and gae_django.py file. http://code.google.com/p/google-app-engine-samples/source/browse/trunk/shell/

from django.dispatch import Signal

request_started = Signal()
request_finished = Signal()
got_request_exception = Signal(providing_args=["request"])