Fix AttributeError on Ajax calls with expired session

When the session expires and horizon does an Ajax call (for example,
to get a modal window), an exception is raised instead of redirecting
to the login screen, because the exception handler in the horizon
middleware doesn't add the "horizon" attribute to the request. This is
a very simple fix to avoid throwing the exception.

Change-Id: I663999dd616b1a4fa3292615eecf3cc44c3e808a
Closes-bug: #1224458
Use a @cached_property decorator

Instead of using an ugly code that uses __dict__ or hasattr,
use a @cached_property decorator that encapsulates the
property caching logic in a single place and makes it easier
to later replace with better caching techniques.

Re-use the cached_property from django.

Change-Id: I9e3e26cd4a8c7055854e851bc5f062a29981971e
Fix django.conf.urls.defaults imports

These imports aren't available in Django 1.6. We need to use
django.conf.urls instead.

Partially-implements blueprint django-1point6

Change-Id: I692439a76de4fe5abff9ab9395bad5c10f1cdbba
Enabled django-compressor for javascript sanity test

By default the test did not run with the compressor on
which did load the javascript. There's no way to test errors
compressing the javascript.

Fix bug #1187576

Change-Id: I1db226ae9709ff818e8d13b7935ded66c0f6eae3
Importing from trove-client compat

Fixes bug #1250237

Change-Id: I7a67fa7e2ab34c960fed908090edb05059ae74e4
Merge "Fix AttributeError on Ajax calls with expired session"
Merge "Use a @cached_property decorator"
Add logging configuration for iso8601 module

iso8601 module outputs log messages but it is not useful for users,
so this commit assigns null log handler to iso8601 module.
This change suppresses iso8601 log messages during unit tests.

Also moves openstack_dashboard related logging config for unit test
from horizon to openstack_dashboard.

Change-Id: I01cf12688118e2137382b8dc7a050b3587749354
Closes-Bug: #1250554
Merge "Fix django.conf.urls.defaults imports"
Merge "Importing from trove-client compat"
Merge "Enabled django-compressor for javascript sanity test"