Author: Juan Leyva
MDL-44342 airnotifier: Use system context instead user.
Added missing capabilities and language strings
http://git.moodle.org/gw?p=moodle.git;a=commit;h=324facf4576902cdb307e3ea6a1c5fe29cbc6546
http://github.com/moodle/moodle/commit/324facf4576902cdb307e3ea6a1c5fe29cbc6546
+ 2.7 en [nopermissiontomanagedevices,message_airnotifier]
+ 2.7 en [airnotifier:managedevice,message_airnotifier]