add first and last aggregator
add first and last aggregator

Signed-off-by: Chris Larsen <83037b211e1d109d6858769a113e269c3139ffd3@yahoo-inc.com>

alienth/opentsdb,MadDogTechnology/opentsdb,alienth/opentsdb,MadDogTechnology/opentsdb,OpenTSDB/opentsdb,OpenTSDB/opentsdb,OpenTSDB/opentsdb,MadDogTechnology/opentsdb