added a few missing components

appengine_django/management/commands/rollback.py

appengine_django/management/commands/runserver.py

appengine_django/management/commands/startapp.py

appengine_django/management/commands/testserver.py

appengine_django/management/commands/update.py

appengine_django/management/commands/vacuum_indexes.py

appengine_django/models.py

appengine_django/replacement_imp.py

appengine_django/serializer/__init__.py

appengine_django/serializer/python.py

appengine_django/serializer/xml.py

appengine_django/sessions/__init__.py

appengine_django/sessions/backends/__init__.py

appengine_django/sessions/backends/db.py

appengine_django/sessions/models.py

appengine_django/tests/__init__.py

appengine_django/tests/commands_test.py

appengine_django/tests/core_test.py

appengine_django/tests/db_test.py

appengine_django/tests/memcache_test.py