[BACKLOG-248] Write extension point plugin producing guava bus events
	- added 2 new attributes to JobEvent and TransformationEvent: startTimeMillis , endTimeMillis
	- startTimeMillis is set with the currentDate.getTime() of the given job/transformation, and endTimeMillis is set upon the triggering of the 'JobFinish' / 'TransformationFinish' PDI Extension point listeners
	- added 3 more PDI Extension point listeners to the monitoring plugin: JobFinishMonitor, TransformationFinishMonitor, TransformationStartMonitor
Merge pull request #686 from pedrofvteixeira/monitoring

[BACKLOG-248] Write extension point plugin producing guava bus events