Author: Shamim Rezaie
MDL-69166 core_payment: helper methods to get cost and to deliver order
Also create the infrastructure to let components know when they have to
deliver what they sold. We are going to use namespace functions instead
of traditional callbacks.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=22c68a8197622e28f9549ecea1e33b3479111007
http://github.com/moodle/moodle/commit/22c68a8197622e28f9549ecea1e33b3479111007
+ 4.0 en [callbacknotimplemented,payment]