Included new section to add floating IPs using dashboard

Updated the 'Configure access and security for instances' section in the
dashboard chapter of the End User Guide to include a new section 'Allocating
floating IP addresses to instances'.
Closes-Bug: #1280926

Change-Id: Id273e9bca078006679dc9b0273634d1220c02ac9
Merge "Included new section to add floating IPs using dashboard"