GEOMESA-113 Change naming scheme to reflect Accumulo version
GEOMESA-109 Refactor IndexSchema

* Broke up the IndexSchema file into separate files.
* Changed the STII's use of an IndexSchema to a IndexEntryDecoder.
* Pushed everything down into the IndexQueryPlanner in preparation for work on it.
Merge branch 'accumulo1.5.x/1.x' of github.com:locationtech/geomesa into accumulo1.5.x/1.x
Merge branch 'accumulo1.5.x/1.x' into wps