Allow custom ELEMENTS_PATH settings.

This allows removing the copied heat-cfntools element.
Delete copied heat-cfntools.
Use progress-capable glance invocation.
Fix security group descriptions
Work around bugs 1089261 and 1247019.

Due to https://answers.launchpad.net/heat/+question/233307 we have to
use an admin account, but admin accounts get both the interior and
exterior network, which means we have to specify the network, but
specifying the network requires a guid due to 1247019.
Workaround bug 1247023

For some reason while the security group is created, nova is refusing to start
the instance with it :/
Switch to Ubuntu.

It's a shame there is so much that needs changing.
Use a generic DNS server.