REFACTOR ALL THE THINGS

To elaborate: Rename all the page/tab group/box models (and their
associated Backbone things, routes, db tables, etc.) to be
templates. Things should be working (the tests pass, and the site
seems to be functional), but bugs may crop up since the test suite is
pretty minimal.

Next thing to do is create the filled-in version of all these models,
and work out the logic to make notebooks properly sharable.
Add filled-in versions of models.
Backend work for notebook templates.

Now we have a template class/model which corresponds to each part of
the notebook hierarchy. When a new user is given access to the
notebook, a parallel hierarchy of instantiated models (PageTemplate =>
Page, etc.) is created and saved. This is then destroyed if the user
is removed from the notebook. This is only on the backed, though -- we
don't have these changes integrated in the Backbone code yet.
Frontend work for notebook templates.

This follows more or less the same structure as the backend does --
for each template model/view, we have a corresponding model/view for
instances of the template. These are all hooked up to the backend, so
we have full functionality now.