standardized PHPDocs package info + fixed copyrights to reflect real author of classes (if anybody wants to change anything I would like to be contacted)

MDL-24090 new detection of plugins that were not upgraded to work with Moodle 2.x (uses $plugin->requires) + bumping ancient versions of plugins

MDL-24089 confirm upgrade of plugins + replaced continue button with 'Upgrade' - this should tell admins when is the upgrade going to really start

MDL-16853 improver set_field() unittests, hopefully this would detect any potential Oracle problems mentioned in tracker

MDL-15916 teachers now control course welcome messages in each course separately, you can also specify custom message

AMOS BEGIN
 MOV [sendcoursewelcomemessage_desc,enrol_self],[sendcoursewelcomemessage_help,enrol_self]
AMOS END

MDL-23899 fixed asort to modify parameter instead of returning array - it now matches standard asort()

MDL-24079 fixing recent regressions caused by api changes in tablelib; sorry I did not find the problem earlier

MDL-24079 fixed recent and old regressions in tablelib, next commit is going to include fixes for usage of tablelib

MDL-24009 fixed wrong file url rewriting and removing cleaning from lesson page contexts - this is marked with RISK_XSS