broke out the object cache functionality; generalized ReadOnlyVector;

finally implemented background sweeps of unreferenced cache objects;
anonymous user, when viewing profiles, now sees them as if all "privacy"
flags were switched on

TODO

@@ -2,20 +2,13 @@ Lots!
 
 - Unimplemented functions on the SIG Administration page:
   Set SIG Features (sigadmin, command=F)
-  View Audit Records (needs to be added)
 
 - Unimplemented functions in the system admin menu:
   Set Global Parameters
   View/Edit Banned Users
   User Account Management
-  View Audit Records (needs to be added)
   (More stuff needs to be added, I'm just not sure what.)
 
-- Should we provide the sysadmin the ability to disable SIG creation for
-  non-admin users?  Maybe there needs to be a "global" set of levels that
-  aren't hardcoded.  Where do they get stored?  The database?  (Maybe the
-  nice shiny new "globals" table?)
-
 - Unimplemented functions on the Top page:
   Customize Sideboxes