Author: Ripal Nathuji
MDL-73767 oauth2: Add clever oauth2 client
http://git.moodle.org/gw?p=moodle.git;a=commit;h=79ae21c23f4b5cd82a6c50218e96aa9cea96d5e8
http://github.com/moodle/moodle/commit/79ae21c23f4b5cd82a6c50218e96aa9cea96d5e8
+ 4.1 en [clever_service,tool_oauth2]