Updates Dev Doc for M3 Release

A few errors in the dev doc were causing problems with deploying
a dev env. The dev dos has been updated with the correct steps for
prep'ing a host for running Kolla. Additionally, wording has been
added to reference the Heat template for dev env deployment.

Change-Id: I9f0ba1bd2deca490a72b3c54cb1a7df386228ee8