Author: Damyon Wiese
MDL-58220 oauth2: Global enable/disable for issuers.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=eca128bf4786a5bd55614525a8fba0be73beaac8
http://github.com/moodle/moodle/commit/eca128bf4786a5bd55614525a8fba0be73beaac8
+ 3.3 en [issuerenabled,tool_oauth2]
+ 3.3 en [issuerdisabled,tool_oauth2]