Fix building the manual with Django 1.6.

This is a trivial change that just switches from calling execute_manager
to execute_from_command_line, in order to build again on Django 1.6.
Don't auto-collapse review boxes that have open issues or drafts.

It was easy to lose open issues after posting a change, since the boxes
would collapse. It was also annoying to have to reopen old reviews that
you were still commenting on (though at least the draft banner was
visible).

We now remove the collapsed state on boxes if they have any open issues
listed (and the viewing user is the author of the review request),
or if there's any draft reviews, making it easier to see the reviews
that still need attention.
Don't load JavaScript extensions on the 404 page.

The 404 page was allowing JavaScript extensions to load, but the
initialization code is expecting the page to have a valid URL resolver.
We really don't want to load them here, so disable the block that
handles the loading.
Upgrade the Django dependency to 1.6.2.

1.6.2 just came out, and fixes a number of bugs. This updates our
dependency to require this version.
selfrequest -> self.request

Trivial typo fix.