To avoid links to OpenStack docs getting out of date in our docs, use
the latest version.

Ideally after cutting each stable branch we should change these links to
use the current release.

Co-Authored-By: Isaiah Inuwa
Change-Id: Ia1e3c720f4e688861b8f76874a3943b0f4e50b17

Change index to ease identify what service want to look.
Split docs into more specific folder such as networking
and storage.

Change-Id: Ic7ac12b3dd555fa5c018eeb897ccd4a5a2dfe8f3