Enable new event scheduler
Use the new event scheduler by default for any users/groups/experiments configured for it using EmulabFeatures. Added '-N' option to eventsys.proxy to have it use the new scheduler (if it exists) instead of the old one. Added test for NewEventScheduler feature to eventsys_control so that it will pass the '-N' option to eventsys.proxy for experiments/users/groups using the feature. These changes will go away when the new event scheduler replaces the old one.