[FEATURE] Log to sys_log when changes are made to scheduler tasks

To keep track of who created what task, introduce logging.

Logging is done for create, edit and delete.

Change-Id: I50003c6a8e9fc68137b06b7c692ba89bad02f87e
Resolves: #34056
Releases: 4.7
Reviewed-on: http://review.typo3.org/9095
Reviewed-by: Joh. Feustel
Tested-by: Joh. Feustel
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Georg Ringer
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch