Add support for quick creation of page templates

Right now if you want to create a new page template that is visible in the Create Page wizard you need to:

• either go to the Wiki Administration / Content / Templates section
  • fill the template provider name
  • click Create
  • fill the "Template Name" field
  • fill the "Template to Use" field (find the page you wish to use as a template)
  • fill the "Terminal Page" field (probably depending on the page selected as template)
• or add the template provider object from object edit mode and fill the fields as indicated above

The issue with this approach is that we loose the context. I believe the normal flow is this:

• create a new page that you wish to make a template or navigate to an existing page
• "mark" this page as template from that page (ideally without navigating away)

Ideally this should not require administration rights. We should probably rely on wiki components to add support for creating user-level templates so that any user can have its own templates visible in the Create Page wizard.