Search functionality is branching out from just being about review

requests. It's time to move the code out into its own app, and to make

/search/ a top-level URL.
This is just code shuffle. Nothing of any substance has changed,

implementation-wise, with one exception. SearchView, it turns out, is

not thread-safe. We now use Haystack's search_view_factory wrapper,

which will instantiate a SearchView for every request, fixing the thread

safety.

Performed searches successfully.