Adding comment_count to blog index.

Adding a comment_count var to the box indexes, so devs can do:

{{ comments:count_string count=comment_count }}

I did use a subquery for this because of the sheer amount of filtering
you need to do to get the right count, so if anyone is not cool with
that, speak now.
Code Formatting

I had line wrapping turned on in Sublime Text 2 and didn't realize I
had a few long code chunks.