[scheduler] Implement container/timesharing/placeholder for the reservations

IO lib bugfix: moldable_id used instead of moldable_job_id
[scheduler] drop scheduler.pm and rework oar_meta_sched

Push Scheduler.pm code to oar_meta_sched (it is only used there)
Remove unused dependency to Scheduler.pm in Hulot
Delete Scheduler.pm
Rework logs in oar_meta_sched
[scheduler] rework logs for the placeholder schedulers