scheduler 5.x-1.17

Notable changes:
- special permission for administering scheduler
- new tab in admin/content/node for viewing all scheduled nodes without views module

The dirty details:
#328688 by ericschaefer: Using format_date() instead of date() for formating of $node->scheduler['published'] and $node->scheduler['unpublished'].
#344138 by syscrusher and jonathan1055: Displaying list of scheduled nodes (contrib)
#344138 by jonathan1055: Adjust column headers of list of scheduled nodes to the usual values
#344138 by jonathan1055: Adjust default ordering of list of scheduled nodes to the usual values
#442554 by ericschaefer: Set permission to change format string to 'administer scheduler'
#442554 by jonathan1055: "access admin pages" is too permissive for allowing user to change scheduler settings (forgot hook_perm)
#442554 by laken: "access admin pages" is too permissive for allowing user to change scheduler settings (forgot a ; this time)...