Ensure the documentation is kept up to date by automatically
generating it from the source when the docs are built.
This patch:
1.replace oslosphinx with openstackdocstheme since oslosphinx is obsolete
2.add oslo_config.sphinxconfiggen to generate sample conf file
3.add oslo_policy.sphinxpolicygen to generate sample policy file
Change-Id: I39f03023f0a85e4c8943925268ab3e9066975630
3cb5c38edb