IndexIterator Work-in-progress

A work in progress branch to address GEOMESA-101 --- adds an IndexIterator that can be used in place of the SpatioTemporalIntersectingIterator. 

This PR is for comments. I'd still like to write a few unit tests for the indexIterator's trigger logic as well as remove the use of JavaConversions.

Not sure what you feel is duplicative: SF_PROPERTY_START_TIME and SF_PROPERTY_END_TIME could point to two different attributes, although their default values are equal. The nesting....has been removed. The new structure makes it more clear that we are first trying to fetch a name, and failing that, check to see if an attribute with the default name exits, in which case we go with the default name.