Author: Andrew Davis
MDL-29615 message: added the ability for admins to restrict users ability to set where their email message notifications go
http://git.moodle.org/gw?p=moodle.git;a=commit;h=84f533b3c34071376775e27a7e2f48b85cabf222
http://github.com/moodle/moodle/commit/84f533b3c34071376775e27a7e2f48b85cabf222
+ 2.3 en [configmessagingallowemailoverride,core_admin]
+ 2.3 en [messagingallowemailoverride,core_admin]
+ 2.3 en [ifemailleftempty,message_email]