GEOMESA-583 Adding customized encoding/decoding for index entries

* Replacing IndexEntry encode/decode with IndexValueEncoder
* Adding ability to specify attributes to encode in st index value to SimpleFeatureTypes, SftBuilder
* Selecting index iterator in the case of a transform covered by the custom index value
* Improving method profiling
Question:  I saw issues with this sort of syntax when deploying GeoMesa in November.  The user-facing complaint was along the lines of, "invalid SRS -1".  Turned out, it appeared to be trying to parse an SRID of "4326:index=true".  Has anyone else ever seen this, or did I just grab RC2 at an awkward stage?