While implementing this, I removed the ~100 lines of very similar code from the top of each question type's editquestion.html template, and moved this to a the function print_question_form_start() in the base class, which uses the template question/type/editquestionstart.html. This is described in more detail here: http://moodle.org/mod/forum/discuss.php?d=51590, and is why this patch makes the codebase 523 lines smaller.
backuplib.php removed backup code related to question_essay_states
type/essay/db/mysql.sql and postgres7.sql removed all SQL
type/essay/display.html improved essay display
type/essay/questiontype.php, editquestion.php, and editquestion.html removed all uses
of the two tables - this resulted in a great simplification of the essay question type