This patch adds a DevStack plugin to cinderlib so it can be installed
directly by DevStack and used for CI jobs as well as development.
When installing it will also get the Cinder configuration and generate a
.py file with the right initialization of the different backends that
have been configured in /etc/cinder/cinder.conf by the DevStack Cinder
job and its plugins.
Change-Id: I12f6b0e1bc047f1915e4f7532ea59495477f9b4a
37c085fd6c