Retitle several documents

We decided during the ODS documentation session that several
documents need retitling.  This patch retitles the documents
but doesn't actually adjust the content.  There is a separate
patch under work which refactors the content from three documents
into one document.

Change-Id: If5a4718b0ab50c405d42a2e20b7b054b93f3227a

doc/heat-dev-env.rst

-A Kolla Cluster with Heat
-=========================
+Development Environment with Heat
+=================================
 
 These `Heat <https://wiki.openstack.org/wiki/Heat>`__ templates will
 deploy an *N*-node `Kolla <https://wiki.openstack.org/Kolla>`__ cluster,

doc/image-building.rst

-Image building
-==============
+Building Container Images
+=========================
 
 The ``tools/build.py`` script in this repository is
 responsible for building docker images.

doc/quickstart.rst

-Quickstart to Deploying OpenStack using Ansible
-===============================================
+Bare Metal Deployment of Kolla
+==============================
 
 Evaluation and Developer Environments
 -------------------------------------

doc/vagrant-dev-env.rst

-Vagrant up!
-===========
+Developemnt Environment with Vagrant
+====================================
 
 This guide describes how to use `Vagrant <http://vagrantup.com>`__ to
 assist in developing for Kolla.