GEOMESA-121 Rewrite input filters with ORs at top.

* Implemented rewriting arbitrary filters in Disjunctive Normal Form.
  This means that any ORs have been 'bubbled up', and any NOTs have been 'pushed down'.

  The resulting filter tree has at most one OR at the very top.
  Additionally, each child of that OR is an AND or a base filter.

* Implemented property-based tests for the filter rewriting functionality using ScalaCheck.

Of note:  A clear optimization is that attribute filters need not be split up or otherwise mangled.
This issue is as https://geomesa.atlassian.net/browse/GEOMESA-171

* Refactored some of the test code to pull data generation.
I believe the two can be used together*.  ScalaCheck allows us to generate additional test cases with ease.  Specs allows us to write a human-readable specification.  

I've had some luck parameterizing specifications.  So far, I've used ScalaCheck for it's generator combinators.  Worst case, I can re-roll that sans the library or use it personally to generate static, hard-coded test cases.