* remove unused css (using purgecss but also checking results manually)
* remove unused fonts
* remove unused examples_schema_migrations dir
* remove underscore & bootstrap pagination
* remove unused djangodocs files
* clean up djangodocs.css
* organize static files (move to _static/scripts and _static/styles)
* clean up and organize scripts (move out of layout.html and into hdocs.js)
* defer scripts that can be deferred
* remove global_tabs extension & files and replace with tabs directive in the only place it's used
