This change moves all the data querying logic out of the review_detail view

into a new ReviewRequestPageData object. The view itself is now primarily

concerned with computation of the etag, creation of the entries, and rendering

of the template--as it should be. This new object documents its attributes, and

is passed into the builtin fields which wish to use it to optimize their

queries, rather than the old locals_vars hack, which I believe was possibly

literally one of the gateways to hell.
As I was doing this I cleaned up some code which was no longer used and moved

some of the work from pre-etag to post-etag. This also changes some of the

timestamp comparisons to work off of integers (ctimes) instead of datetimes,

since before we had a few instances where we were comparing datetimes to 0.

Did lots of testing with a few different review requests with lots of change

  description and review boxes.
Ran unit tests.