ADD: new plugin ref_urls.

* This is similar to the pages/access.php solution, but does not require URL
  rewriting; furthermore, the scrambled paths are hidden completely.
* Using this plugin, it is no longer needed to have the filestore accessible
  from the web.


git-svn-id: http://svn.montala.net/svn/resourcespace@5053 c08608d7-6e46-0410-86ca-f2a6f1370df5
CHG: Further optimisation to the new UNION/bit_or() code so it uses a join at the outer level instead of a comma - a further 25% reduction in execution time on our query 


git-svn-id: http://svn.montala.net/svn/resourcespace@5054 c08608d7-6e46-0410-86ca-f2a6f1370df5