enable/disable scripts for all users. filter own/all jobs.

 * Scripts are now enabled/disabled for all users, not only guests.
 * The enable/disable scripts widget has been moved into its own admin settings tab.
 * In the jobs list, admins now only view a list of their own jobs by default, but can click "show all jobs" to show jobs from other users as well.
Merge branch 'improved-scripts-and-jobs-filtering'