Updates to the 'Launch a stack' section
Updates to the 'Launch a stack' section

Updated the following:
- Included new procedure to 'Manage a stack'.
- New steps to select the template and environment sources for the stack.
Partial-Bug: #1307860

Change-Id: I5fab0587ce7a81e5092f9e089b4cbb2197c7b8d0

openstack/openstack-manuals,saeki-masaki/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,Akasurde/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,potsmaster/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,gongysh2004/openstack-manual,kairoaraujo/openstack-manuals,gongysh2004/openstack-manual,potsmaster/openstack-manuals,saeki-masaki/openstack-manuals,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,Akasurde/openstack-manuals