Use Django's smarter if tag.

Django these days provides a smarter if tag that allows for basic
expressions. This is nicer than using ifequal for things, and with
Django 1.4, we can also do elif. This cleans up bits of the code and
allows some expressions and nested ifs to be condensed.

I checked a few pages, but haven't checked everything. I'd like a pair
of eyes on every line of my change to be sure I didn't do something
stupid. We'll also want to just test this a lot before beta.