By MICHAEL PORTANTIERE for Theater News An exhibition of Hilary Knight's original artwork for Eloise Takes a Bawth, including some drawings that were not used for the book and three new Eloise prints, will be presented by Giraffics Gallery of East Hampton at (where else?) the Plaza Hotel in Manhattan on Friday and Saturday, November 29 and 30, from 12 noon to 5:30pm. Knight will be present on both days, from 2 to 4pm, to sign books and prints purchased at the event. The lates