Feature/refactor css

In the process of poking at other issues, I became a bit frustrated with the mess of tags to load CSS in the templates. The same style sheets were being loaded in different places in different orders, certain stylesheets were being loaded unnecessarily, etc. In addition, the stylesheets were being redundantly minified for production by both django-compressor and django-require. 

This PR removes all of the {% compress css ...%} blocks in favor of css imports organized by component (base, exhibit display, edit, details, etc.).

In addition, it fixes a couple of bugs in the process. In particular, the titles for list lenses weren't being rendered correctly, and bootstrap CSS was being loaded in embedded views unnecessarily.

Finally, some outdated jquery UI themes are deleted.