Author: David Mudrák
MDL-51261 admin: Add option to define upgradekey via cli installer
http://git.moodle.org/gw?p=moodle.git;a=commit;h=6ef02f847978c4b29345ee6be51c556fc0810adf
http://github.com/moodle/moodle/commit/6ef02f847978c4b29345ee6be51c556fc0810adf
+ 3.0 en [upgradekeyset,core_admin]