Moved openstack env variables out of snapcraft.yaml, and into a
"microtack.rc".
Made openstack-wrapper, which auto sources microstack.rc.
Key off of revised snap.openstack, which supports snapctl config
values in templates. Moved a lot of the overlay into
snap-overlay/templates, and added config values to them. Also writes
templates just once, when you run snap-openstack setup.
Change-Id: Ib0f2e3fc97f491d9ed9dfbafc61dc8e27a8a2b48