'Save' and 'Publish' buttons change on the fly.

The label is chosen based on the action. Already published
article can only be saved, while on 'pending' and new
articles  the button changes based on the new selected
status.

This change also adds '.published' and '.saved' classes to
the #article_form.

Closes issue #53

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5561 2fea6a4d-a838-0410-917b-93a53c48e9d2