Notification of string changes

Author: Huong Nguyen
MDL-71953 calendar: Accessibility improvement for manage subscription
- Create new web services for manage subscription (Update calendar subscription)
- Modified delete subscription feature to use Web service.
- Midified update subscription feature to use in-place editbale
- Delete subscription feature now have a confirmation box before processing.
- Fixed some accessibility issues
- Used 'Delete' instead of 'Remove' for deleting subscriptions


http://git.moodle.org/gw?p=moodle.git;a=commit;h=bca6b06a1c9be394c59ee70be3bb2f9e4730f20b
http://github.com/moodle/moodle/commit/bca6b06a1c9be394c59ee70be3bb2f9e4730f20b

+ 4.0 en [colpoll,core_calendar]
+ 4.0 en [confirmsubscriptiondelete,core_calendar]