Circa Date: Saving and Exhibit Rendering

Timeline and exhibit circa date checkbox choices (Edit Timeline and Edit Exhibit panes) are now saved to and read from the database, as well as being stored in ChronoZoom's virtual canvas so that they are immediately rendered without a page refresh.

Exhibits with a circa date now render with a dotted outline, to indicate that the date is approximate, in browsers that support this functionality. (Tested OK with latest IE, Chrome and Firefox.)

Possible follow-up check-in will render the left border or right border of a timeline with a dotted line too, if the from date or until date of a timeline is approximate.