All comments on a review have the same basic structure, which is

repeated for each type of comment. We've kept it this way for a while in

an attempt to avoid the overhead of including another template for each

comment, but it's getting difficult to update those, and we're pretty

good at caching these days.
This change splits off the common bits into a new

reviews/entries/_review_comment.html template, which handles

everything but the context above the comment. Rather than going with a

more complex solution of subclassing a base comment template for the

context, or having Python-side comment renderers, we're just having the

main _review_body.html template define a variable with the context

before including the common template, which works fine and keeps it

maintainable and a little faster.

Tested every type of comment. Made sure each displayed correctly and

could be replied to.