This change does the work necessary to move us to a modern django-pipeline.

This involves several independent but related pieces:

- Bump the dependency.

- Update existing templates to use the new pipeline templatetag library and

  associated stylesheet and javascript tags.

- Add a compatibility library for third-party packages that still want to use

  the old compressed tag library.

- Change settings.py to use the new PIPELINE structure and split out static

  media into a staticbundles.py file.

- Make changes to everything that manipulates settings.PIPELINE* to use the

  new settings mechanism.

- Make a few changes to the staticfiles finders and loaders to cope with

  pipeline's "simplification".
This requires django-pipeline 1.6.6, which contains several patches to fix bugs

and add features that we need for this.
This also adds the very beginnings of 0.10 release notes to include

compatibility instructions when updating to use this.

Ran unit tests
Built a djblets package and verified that static media got compiled correctly.
Explored through the Review Board UI and checked that both the basic UI and

  extensions which shipped static media worked correctly.
Built an extension and saw that everything worked correctly.