Expose r/o listener callback + details filter callback
Expose r/o listener callback + details filter callback

Also makes sure that the kwargs that are returned are
not mutable by returning a copy (which if modified will
have no effect).

Change-Id: I1d04e2084cbf93d876e946b2bd6466a4b700faad

jimbobhickville/taskflow,pombredanne/taskflow-1,openstack/taskflow,openstack/taskflow,junneyang/taskflow,pombredanne/taskflow-1,junneyang/taskflow,jimbobhickville/taskflow