Move around the development environments

THe top level dev directory is now used to store the heat and
vagrant development environments.

backport: liberty

TrivialFix

Change-Id: Ib0922b90eacaa8518aee09cdeb46f4ac0437e015

README.rst

@@ -70,7 +70,9 @@ Directories
    community members which want to use Kolla container content without
    Ansible.
 -  demos - Contains a few demos to use with Kolla.
--  devenv - Contains an OpenStack-Heat based development environment.
+-  dev/heat - Contains an OpenStack-Heat based development environment.
+-  dev/vagrant - Contains a vagrant VirtualBox/Libvirt based development
+   environment.
 -  doc - Contains documentation.
 -  etc - Contains a reference etc directory structure which requires
    configuration of a small number of configuration variables to achieve
@@ -80,8 +82,6 @@ Directories
 -  specs - Contains the Kolla communities key arguments about
    architectural shifts in the code base.
 -  tests - Contains functional testing tools.
--  vagrant - Contains a vagrant VirtualBox-based development
-   environment.
 
 Getting Involved
 ================