Allow "self" as a value for "root".  Refs #8962.
Allow "self" as a value for "root".  Refs #8962.

When including a Gantt in a ticket description, `root=self` will show
the children without an explicit ticket ID.  This is useful in ticket
templates and when cloning tickets so they don't need to be edited.

Thanks to bof for the patch!

git-svn-id: 2159781fc7c14c6bdd1f7e265daf7a25099c31e7@10408 7322e99d-02ea-0310-aa39-e9a107903beb

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