Pending events

An initial stab at issue #174
 * similar to events, creates a pending_events table
 * similar to telling the agent to create an event, you can tell the agent to queue_event
 * HuginnScheduler monitors the table every minute, adds jobs to rufus when new pending events are seen

Still a couple of things to do, but I wanted to get some feedback first. Things I am aware of:
 * handling server restarts when we scheduled the task with rufus 
 * specs, duh