MDL-8323 finished full conversion to proper $COURSE global - no more $CFG->coursethem...

MDL-8323 finished full conversion to proper $COURSE global - no more $CFG->coursetheme, $CFG->courselang - improved course_setup(), current_language() and current_theme(); and Chameleon theme fixes needed for global $COURSE
MDL-7962 chat seems to be completely broken in head (fixed wrong JS)
* reworked chat themes support
MDL-8338 Cron does not need cookies
MDL-8339 forum cron capabilities problems
* minor deprecated function current_encoding() cleanup