This change makes it so that the header field opens into an editor by default,

except in the case where there's some saved text in there already. This is done

because usually if someone is opening that dialog, it's to add some general

commentary. We might revisit this once the general comments work is done.
While I was in here, I noticed that the label for "Ship It" wasn't lining up

properly with its checkbox, because a CSS rule was too general and was making

it into a block element. I've fixed the rule to be more specific.

Review dialog with no comments: open editor for the header.
Review dialog with some comments: open editor for the header.
Review dialog with pre-existing header text: closed editor.