minor code review changes
GeoBoundsAggregator now extends a new type of aggregator, LeafAggregator.

A LeafAggregator does not filter or count documents. Nor does it support sub aggregations. MetricsAggregator is a subclass of LeafAggregator
Added option to allow wrapping of longitude

This means that the bounding box will overlap the date line if the bounding box would be smaller than not overlapping the dateline
Refactored BoundingBox
Documentation changes to add leaf aggregations.

Still need to add explanation of what a leaf aggregation is in the aggregations section
better variable naming