Handle implicit dates in parent tickets.  Refs #9042, #9515.
Handle implicit dates in parent tickets.  Refs #9042, #9515.

Need to carry around an indication of whether the date is implicit or
explicit.

git-svn-id: 2159781fc7c14c6bdd1f7e265daf7a25099c31e7@11069 7322e99d-02ea-0310-aa39-e9a107903beb

trac-hacks/trac-jsGantt,trac-hacks/trac-jsGantt,trac-hacks/trac-jsGantt