Adding Javadoc to async binding interfaces
Adding overrides of write protocol async methods to do the same logging as their synchronous counterparts
Sharing transformer for findAndModify-based operations via a FindAndModifyHelper class
Using serverIsAtLeastVersionTwoDotSix in CreateIndexesOperation.
Also changed variable name from retVal to future.
Added executeAsync to DistinctOperation
Normalisation of apply signature
Added executeAsync to AggregateOperation and AggregateExplainOperation