orchestration add basic support for environment API test

Adds support for passing environment into create/update API calls,
and implements a basic test which proves a parameter can be passed
via an environment.

These links document this interface, which is currently not tested
in tempest:
http://api.openstack.org/api-ref-orchestration-v1.html
http://docs.openstack.org/developer/heat/template_guide/environment.html

Change-Id: Id3e3a69370603d5a700ef0d0b1dcb09a3765b09f
Partial-Bug: #1317095
Merge "orchestration add basic support for environment API test"