Show TOC in side bar
Show TOC in side bar

The current sidebar only has a link "Contents" and
provides almost no information.
It looks reasonable to show TOC in the sidebar.
openstackdocstheme 1.5.0 has an option 'sidebar_mode'
and it allows us to show TOC in the sidebar.

Change-Id: I97b7f4d67053bf065ae0035acf7b973b9450eeb2

openstack/training-guides,openstack/training-guides