change to section_dashboard_admin_manage_images

it should be minimum RAM not disk validated in horizon

Change-Id: I264234a0f649e6de400af4afd9b0a78759a2902b
Document that nova-network and VDS port group must be ephemeral

Add content clarifying that the port binding for the br100 port
group must be configured as ephemeral in vCenter. Included link
to a KB article that discusses port bindings.

Change-Id: I5bc2dcad56a8e6e54bb4a7476c89cbcaff6970aa
Closes-Bug: #1270306
Merge "change to section_dashboard_admin_manage_images"