Provide "Server Starting" in the administration console during startup.

When a Couchbase Server node is starting with lot of data it could takes
some times until the administration console is ready to respond to
request. This could be somehow disturbing to the user.
I would suggest the following improvement, if possible

• start the HTTP Server (Admin Console) as soon as possible
• provide a default page with a very simple message "Server Starting...."
• refresh the page periodically (not "too much") until the console is
  available (or do a push)