Adjust page prototypes

To demonstrate the new Page Management features in the archetype, please implement the following:

• Rename the template “no-document-prototype” to “Single column”
• Add a second template “Two column” with the two identically sized columns occupying the same space as the single one (see https://docs.google.com/a/1hippo.com/document/d/15tJswbiY0sXQYxxxY6T7WEfvlSIClUphQalG0EIVW50/edit#)
• Only newly added pages must be “editable”
• The menu visible on the home page must be editable (no more work there)