The extras module contains functionality that is not often used. It holds
following functionality:

 - switch view modes: switch view mode on a per node basis.
 - block region: add regions which will be exposed as blocks.
 - extra fields: expose extra fields defined by other modules.
 - field permissions: add view permissions on DS fields.
 - Flag: expose flags as fields
 - Hidden region: region which in case it has fields will not be printed.
 - field templates: overwrite any field with custom markup.
 - switch view mode field: switch from one view mode to another inline.
 - page title options: hide the page title or manually set (with substitutions).
 - contextual links: add the 'manage display' link to contextual links 
   and on the full page view of nodes, users and terms.
 - Views displays: render views (row fields) into a different layout.
     Important: If you are creating new ds fields for vd,
     check ds_vd_render_title_field() how to return the content.
 
Any other functionality will be included in this module.