Updated openstack/openstack
Project: openstack/heat  57f141d04ff596954756d092cbfabe394f00b33b

Move implementation_signature to StackResource

We need to use common logic for the update determination which
uses implementation_signature, so move the common code from
TemplateResource to the StackResource base-class.

Change-Id: Ibd64b3607721487be5b0562cdb54e6c76db51149
Partial-Bug: #1389499