GEOMESA-6 Secondary Indexing (PR for comments)

Starting this PR for comments contains code from GEOMESA-169 that will be removed after PRs 107,108 are merged. I'll squash things up later.

The table format changes. Each store has a "Catalog Table" to store feature metadata then three tables per SFT:
1. Attribute Index - Inverted attribute index of simple feature values
2. Record Table - Records only (contains rows referenced by inverted index)
3. ST Index - same as before (spatiotemporal index)

Only equalTo and like queries with trailing % should hit the attr index

AccumuloDataStore is backwards compatible with the old table format (only ST with metadata) and will respect that.

Other Notes:
* Haven't updated the GeoMesa pages yet for multiple tables...that'll come in the next PR

Please comment :)
A writer appears to be a thing with a function SimpleFeature => Unit.

As a cleaner idiom, on construction, create a List[SimpleFeature => Unit].  No need to have a 'null' here, and no need to check the Boolean 'multiIndex' later. 

When writing, map over the List and apply to the SimpleFeature.