Fix misuse of super
Add review queue
Ensure that ForeignKeys to proxy models work
Add view_instance property to widgy views

This gives us an API for widgy's authorization framework.
WidgySite.authorize needs a view instance, so we need to know the view
instance from the view callable.
Enable the review queue on the demo site
Add Api tests for review queue
Add SCSS file for unapproved_commits admin layout
Fix layout for Review Queue
Add widgy siteperms template tag

This allow us to access WidgySite.authorize framework from the template.
Make the review queue a contrib app

Pulled out from core and put into its own contrib app.

Signed-off-by: Antoine Catton <acatton@fusionbox.com>
Remove useless method overriding
Remove WidgySiteTestMixin

We only need it in a single test -- just do it there.
Add model-based permissions API on WidgySite.

The following API views now check permissions:

-  ContentView.put checks change permission
-  NodeView.post checks add permission
-  NodeView.put checks change permission
-  NodeView.delete checks delete permission
-  ShelfView.get filters results based on add permission
-  NodeTemplatesView.get checks change permission
-  NodeParentsView.get checks change permission
-  NodeEditView.get checks change permission on Node
Added UnsafeHtml Widget.

This Widget is unsafe because it provides a potential for permission
escalation.  No non-superuser should have the following permissions:

-  page_builder.add_unsafehtml
-  page_builder.change_unsafehtml
-  page_builder.delete_unsafehtml
Added ReviewQueueViewsTest
Popup improvements

commit 88180d869994e5ccf3a1374da8eae23bb23d0190
Author: Rocky Meza <rocky@fusionbox.com>

    Fixed extra single quote

commit 07dc09cf80c6c971355e2042ec436b5b3b142047
Author: Rocky Meza <rocky@fusionbox.com>

    fixed pop up headers

commit 7aa687c4946c35e1f2885863c05c4d1052f43e8c
Author: Gavin Wahl <gwahl@fusionbox.com>

    Popup improvements

      - adds widgy/popup_base.html
      - adds a loading spinner to the submit buttons
      - prevents double submissions
Added permission checking to versioning views

Also replace siteperms with has_*_permission.
Rename WidgySite.authorize to authorize_view

This communicates its meaning more clearly now that we have the
model-level permissions.
Merge some interdependent features:

  - Review Queue
  - New permissions API
  - UnsafeHtml widget
  - Base template for popups

  Rename WidgySite.authorize to authorize_view
  Added permission checking to versioning views
  Popup improvements
  Added ReviewQueueViewsTest
  Added UnsafeHtml Widget.
  Add model-based permissions API on WidgySite.
  Remove WidgySiteTestMixin
  Remove useless method overriding
  Make the review queue a contrib app
  Add widgy siteperms template tag
  Fix layout for Review Queue
  Add SCSS file for unapproved_commits admin layout
  Add Api tests for review queue
  Enable the review queue on the demo site
  Add view_instance property to widgy views
  Ensure that ForeignKeys to proxy models work
  Add review queue
  Fix misuse of super