Run initialize() in test setUp() methods.

In Django 1.6, the test Client.login() method no longer uses a request, which
means that our middleware that loads the siteconfig isn't guaranteed to run.
For one of our tests, it was hitting the case that the user would be
authenticated against ModelBackend, and then when we tried to do an actual
request, it would load the siteconfig, replacing
settings.AUTHENTICATION_BACKENDS. Once this happened, it would check that
user.backend was in the loaded backends, and when it wasn't, set request.user
to be AnonymousUser.

I've solved this issue by calling initialize() inside TestCase.setUp(). A lot
of our TestCase subclasses weren't calling the super class' setUp(), so I've
fixed that.

This change isn't required on Django 1.5, but it is backwards compatible. I'm
submitting it now so we can get it in and reduce the size of the Django 1.6
patch.

Testing done: Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/5312/
Add a Backbone collection for filtering other collections.

This adds RB.FilteredCollection, which presents a filtered view of
another collection. FilteredCollection takes a dictionary of filters,
which map field names to values. For string fields, the prefix will be
compared, and for other values, direct comparison is used. This can be
expanded as needed down the road to do more complex matches.

When the main collection updates, the FilteredCollection will update as
well, according to the filter.
Add some infrastructure for JavaScript-controlled config pages.

This is a port of some of the code in RBCommons used to handle the
admin and My Account pages. It provides some CSS and JavaScript to
display lists of items with optional actions for config pages.

This is, for now, intended to be a subset of the infrastructure used in
RBCommons, and is just enough for the new My Account page. Going
forward, we'll likely extend this for new bits of UI and things like
better dynamic loading of data.