KNL-1011 - Fix lazy-loading/caching bug in performance improvements

This fix ensures that fully/partially loaded sites are tracked properly,
that the cache is updated when sites are saved, and that the user-site
cache is purged for updated sites.

Note that this change reverts r120432, so both will be required for
merges.



git-svn-id: https://source.sakaiproject.org/svn/kernel/trunk@120433 66ffb92e-73f9-0310-93c1-f5514f145a0a