Fix #773 - Add global_annotations to graphs
Fix #773 - Add global_annotations to graphs

Fixed a bug in which global_annotations were ignored by
GraphHandler.java (and thus, were not rendered by gnuplot). Added async
call to hbase to retrieve global annotations when required in a similar
fashion as that of QueryRpc.java.

Note: Since both GraphHandler.java and QueryRpc.java implement (similar)
query-processing logic, all of this should be unified in the future
(requires a large refactor to split all query logic with visualization
logic).

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

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