This removes all of the heat code from the devstack tree, in favor of the
devstack plugin in Heat's tree.
Depends-On: I4bed1e5cef5afa7b049b07640086a86a3f881e13
Depends-On: Ic392bcc24bc374ee8511a94f1d8f6ac23131c7e3
Change-Id: I5b60422bf1f5fa78aa8f3383f7a222e0356d9e42