MDL-14208 Cache results of calculations, "recompute now" functionality -- added message about when the stats were last calculated and how many attempts there have been since then and a recompute now button.

MDL-15818 "allow quiz reports to register cron routines" - Quiz reports can now include files cron.php which include functions quiz_report_{reportname}_cron that will be executed from the moodle cron. They must also modify their quiz_report record to set cron to the number of seconds between cron execution.

MDL-14216 "change query to work on Postgres." - some adjustments to make it work on mysql again too.

MDL-15813 "return params or a param from moodle_url params and param method when no value is passed to method to set url param(s)."

Methods param and params can now be used in the following ways :

$url->params(); // returns params

$url->params($arrayofnewparams);// add params to url params and then returns all the params.

//--

$url->param('id');//returns value of id param.

$url->param('id', 5); set id param to 5.

MDL-14731 Improved Bryce's patch and applied. YUI version number is kept in a simple version.php file, to be updated manually when updating the YUI libraries.

MDL-14208 'Improvement of Item Analysis Report :  Cache results of calculations, "recompute now" functionality' - using new tables to cache stats results.

This new messaging system replaces all the various email_to_user() calls.
They are now replaced by events triggers, and the messages are then
processed centrally according to user preferences and sent to one or more
processors (email, popup, jabber etc...)

This code is not finished yet, a lot of work still has to be done on the
interface.  However, the basic structure is there and should be working.
Luis and I will be reviewing and polishing this heavily in the next few weeks.

MDL-14650, create a new table `chat_messages_current` to save latest 8 hours messages, could improve performance. The expired message will be deleted in chat_cron function

Was not handling adding subcategories properly. Thanks to Dennis Protzek for the patch.

Merged from STABLE_19

Misused get_role_users() was not returning users assigned in parent categories

Merged from STABLE_19

MDL-13766, rewrite ajax client code, encapsulate all javascrpt code in repository class, which is easy to reuse now.

MDL-15792 - Images in question don't display. This is a regression from MDL-14279. Fix thanks to Yolanda Ordóñez Rufat.