Clean up DB docs - Inclusions in the Confluence setup wizard

"The three pages underneath the confluence setup guide should be removed, and their content included into the page about setup wizard."

The pages are:

• http://confluence.atlassian.com/display/DOC/External+Database
• http://confluence.atlassian.com/display/DOC/Load+Content+for+the+Site
• http://confluence.atlassian.com/display/DOC/Restoring+from+Backup+During+Setup

Notes:

Mon 15 April 2013:

• Already removed "External Database" in a prior cleanup.
• Did a search to find all pages that include the other 2 guides. Only the "Confluence Setup Guide" includes them. Safe to merge and delete.