Compute and controller templates without merge.py

This provides three templates: overcloud-without-mergepy.yaml,
compute.yaml and controller.yaml. These can be used in combination with
overcloud-resource-registry.yaml to deploy the overcloud on their own --
without having to do any pre-processing (via merge.py).

To test these you have to add the resource registry environment (in
addition to the existing `-e` option) and use the new overcloud template
in the Heat call in devtest_overcloud.sh (line 374):

    heat $HEAT_OP -e $TRIPLEO_ROOT/overcloud-env.json \
        -e "$TRIPLEO_ROOT/tripleo-heat-templates/overcloud-resource-registry.yaml" \
        -t 360 \
        -f $TRIPLEO_ROOT/tripleo-heat-templates/overcloud-without-mergepy.yaml \
        -P "ExtraConfig=${OVERCLOUD_EXTRA_CONFIG}" \
        $STACKNAME

The existing overcloud Heat environment
($TRIPLE_ROOT/overcloud-env.json) should keep on working.  Scaling is
now being controlled by the `ControllerCount` and `ComputeCount`
template parameters, though.

NOTE: the changes here depend on a fairly recent Heat build (commit
e5f285f6cb from ~7th September, 2014). In other words, this requires
Juno Heat.

Also, passing more than one environment file to Heat requires
python-heatclient version 0.2.11.

Change-Id: I687a00c7dc164ba044f9f2dfca96a02401427855