schema update.

Fixed a serious bug in List View that printed nodes too many times

*  Try to change hardcoded switch-case statements to callbacks where it
   makes sense to allow modules to extend functionality.
*  Re-factor sorting info so that it goes into the table data and is assembled,
   rather than being hard-coded as it is now.
*  Create on-the-fly filtering too
*  Allow a NOT in the and/or algorithm.
*  description field for view
*  Add changed field to prevent multiple admins from saving views simultaneously

utility of list view

used a flexible callback method so that future functionality can easily
be added!

menu items.