Synnefo

Update guides to reflect new Astakos defaults

• ReCAPTCHA is no longer enabled by default
  (move from Quick Install Guide to Admin Guide)
• Only the 'local' IM module is enabled by default
  (no need to set it during Astakos configuration any more)

Update the Admin Guide

Update the general Admin Guide with a new skeleton.
Moved the old content in the new sections, so that it can be
reviewed and adjusted accordingly.

Also added the Synnefo General Architecture graph in the index
page and the Admin Guide.

Update quick admin quide for RabbitMQ installation

Update guide for ganeti build process

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

Update quick-admin-install-guide for backend-add

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>