Author: Damyon Wiese
MDL-34498 session: Add a checker to warn before session expiry
Replaces old yui module checknet.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=7aeeb44463cf1ddf4f34be0d139427da18d91459
http://github.com/moodle/moodle/commit/7aeeb44463cf1ddf4f34be0d139427da18d91459
+ 3.8 en [sessionexpired,core_error]
+ 3.8 en [extendsession,core]
+ 3.8 en [sessionforceclean,core]
+ 3.8 en [sessiontimeoutsoon,core]