Remove lib/dib

diskimage-builder is a utility rather than a service, and is already
installed in devstack via pip when required.

lib/dib was created to allow an image to be created during a devstack
run for the heat functional tests, however this approach is no longer
being taken and there are no other known uses for lib/dib.

This change removes lib/dib and moves the pip mirror building to
lib/heat so that snapshot pip packages of the heat agent projects can
be made available to servers which the heat functional tests boot.

This also removes tripleo-image-elements, which has never
been utilised, and since images won't be created
during heat functional test runs it is no longer required.

Change-Id: Ic77f841437ea23c0645d3a34d9dd6bfd1ee28714
diff --git a/stackrc b/stackrc
index cb044b8..efea1e4 100644
--- a/stackrc
+++ b/stackrc
@@ -419,14 +419,10 @@
 
 ##################
 #
-#  TripleO Components
+#  TripleO / Heat Agent Components
 #
 ##################
 
-# diskimage-builder
-DIB_REPO=${DIB_REPO:-${GIT_BASE}/openstack/diskimage-builder.git}
-DIB_BRANCH=${DIB_BRANCH:-master}
-
 # os-apply-config configuration template tool
 OAC_REPO=${OAC_REPO:-${GIT_BASE}/openstack/os-apply-config.git}
 OAC_BRANCH=${OAC_BRANCH:-master}
@@ -439,10 +435,6 @@
 ORC_REPO=${ORC_REPO:-${GIT_BASE}/openstack/os-refresh-config.git}
 ORC_BRANCH=${ORC_BRANCH:-master}
 
-# Tripleo elements for diskimage-builder images
-TIE_REPO=${TIE_REPO:-${GIT_BASE}/openstack/tripleo-image-elements.git}
-TIE_BRANCH=${TIE_BRANCH:-master}
-
 #################
 #
 #  3rd Party Components (non pip installable)