Author: Paul Holden
MDL-83259 sms: define plugin type strings and fix management URL.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=246429e89a0e15722353feee11bf0242cd4f15c4
http://github.com/moodle/moodle/commit/246429e89a0e15722353feee11bf0242cd4f15c4
+ 4.5 en [type_smsgateway,core_plugin]
+ 4.5 en [type_smsgateway_plural,core_plugin]