Bug 13889: Add information about cron jobs to system log

Bug 13889: Add information about cron jobs to system log

This patch adds information about cron jobs performed and make it viewable
under Home > Tools > Logs ("Browse system logs")

To test:

Apply patch
- Got to system preferences and set 'CronjobLog' to:  [Log] information from
  cron jobs.
- Run some cron jobs
- Go to Home > Tools > Logs
- Verify that you have a selection 'Cron jobs' in drop-down 'Module'. Select it
  with Action "All" and Submit.
- Output should show Date/time and info about Cron jobs

Rebased to work on top of Bug 6911 (conflict in viewlog.tt)  /MV

Rebased after applying patch for Bug 6911 /MV
Conflicts resolved:
misc/cronjobs/overdue_notices.pl
misc/cronjobs/cleanup_database.pl

Signed-off-by: Frederic Demians <f.demians@tamil.fr>
  - Merge both patches, and fix updatedatabase.pl
  - Works as described. Provide intersting feedback from cronjob scripts.

--
Modified version taking in account syspref CronJobLog. Handling simplified by introducing a convenience sub cronlogaction in C4/Log.pm /MV
Amended to take in account comments #11, #12, #13 /MV

http://bugs.koha-community.org/show_bug.cgi?id=13899

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>