[install-guide-rst] Update draft-index page
[install-guide-rst] Update draft-index page

Add RST Install Guides to draft-index page.

Update HA Guide entry to mention RST conversion.

implements bp installguide-liberty
Change-Id: Ifdc11d5d61ea018cc3872f6bbc2fadbd0aefa00f

AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals,potsmaster/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,kairoaraujo/openstack-manuals,saeki-masaki/openstack-manuals,potsmaster/openstack-manuals,openstack/openstack-manuals,saeki-masaki/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,Akasurde/openstack-manuals,kairoaraujo/openstack-manuals