Refactor Django helpers (googleapis#546)

* Move all Django code into contrib.django_util.
* Add DjangORMStorage. This is backwards compatible with old django_orm storage.
* Add new functionality to decorators and views that integrate with Django ORM-based storage.
* Fix issue where Django storage always creates new Models.
* Move tests into Django package and have them create an actual test app to create test databases etc.
* Remove FlowField.

Author: waprin

docs/conf.py

@@ -12,7 +12,7 @@
 # settings module and load it. This assumes django has been installed
 # (but it must be for the docs to build), so if it has not already
 # been installed run `pip install -r docs/requirements.txt`.
-os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.contrib.test_django_settings'
+os.environ['DJANGO_SETTINGS_MODULE'] = 'tests.contrib.django_util.settings'
 import django
 import mock
 from pkg_resources import get_distribution

docs/source/oauth2client.contrib.django_orm.rst

@@ -0,0 +1,7 @@
+oauth2client.contrib.django_util.models module
+==============================================
+
+.. automodule:: oauth2client.contrib.django_util.models
+    :members:
+    :undoc-members:
+    :show-inheritance:

docs/source/oauth2client.contrib.django_util.models.rst

@@ -8,6 +8,7 @@ Submodules
 
    oauth2client.contrib.django_util.apps
    oauth2client.contrib.django_util.decorators
+   oauth2client.contrib.django_util.models
    oauth2client.contrib.django_util.signals
    oauth2client.contrib.django_util.site
    oauth2client.contrib.django_util.storage

docs/source/oauth2client.contrib.django_util.rst

@@ -16,7 +16,6 @@ Submodules
    oauth2client.contrib.appengine
    oauth2client.contrib.devshell
    oauth2client.contrib.dictionary_storage
-   oauth2client.contrib.django_orm
    oauth2client.contrib.flask_util
    oauth2client.contrib.gce
    oauth2client.contrib.keyring_storage