Link to latest version
Link to latest version

Right now the version drop down links to "Current" which is always the
current version. This is IMHO useless, replace it with a link to
"latest" to link to the most recent version.

Change-Id: Ic221f9a1b10ddee2143d95f69bd56679793c884b

openstack/openstackdocstheme,openstack/openstackdocstheme,openstack/openstackdocstheme,openstack/openstackdocstheme