turn on intersphinx mapping & autosectionlabel exts for docs

[jputrino]

add the following to docs/conf.py

• sphinx.ext.autosectionlabel needs to be added to extensions
• configure intersphinx map to point to other f5 doc sets

intersphinx_mapping = {'heat': (
    'http://f5-openstack-heat.readthedocs.io/en/latest', None),
    'heatplugins': (
    'http://f5-openstack-heat-plugins.readthedocs.io/en/latest', None),
    'lbaasv1': (
    'http://f5-openstack-lbaasv1.readthedocs.io/en/1.0/', None),
    'lbaasv2': (
    'http://f5-openstack-lbaasv2-driver.readthedocs.io/en/latest', None),
    'agent': (
    'http://f5-openstack-agent.readthedocs.io/en/latest', None),
    }