Base attributes don't displayed in documentation

[Peter Razumovsky]

Currently documentation generation doesn't handle base_attributes_schema of Resource class, so end-user can't learn any base attributes.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/212635

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/212635
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=361f5acb3a1cedae7a31ba1069fd9fc0658d1d37
Submitter: Jenkins
Branch: master

commit 361f5acb3a1cedae7a31ba1069fd9fc0658d1d37
Author: Peter Razumovsky <email address hidden>
Date: Thu Aug 13 19:33:18 2015 +0300

    Add base_attributes_schema to documentation

    Currently base_attributes_schema omitted in docs,
    so there's no chance to learn about base attributes.
    This patch adds base_attributes_schema to docs and
    fixes description of "show" base attribute.

    Change-Id: Id382e39401d368367f1813e7f9e4508d4dffef72
    Closes-bug: #1484142