DIMITRI: Unify nav and headers across legacy pages (Fixes #62)

Fixes #62. Notably:

- A new tag (`include_static_file`) is used to include an Angular bundle to drive the new header and footer.
- Red Bull headers and footers removed.
- Some legacy CSS classes removed in favor of new Angular app styles.
Oh, I guess it should be! Then we don't have to maintain this in two places. :+1:

(The footprint of the vendor.js and scripts.js files is so small that I don't mind inserting them on all Django pages.)