GEOMESA-74 Change Geoserver Plugin to hide password

PR # - Base_Branch:master
GEOMESA-75 Change Geoserver Plugin to allow blank Auths param
GEOMESA-73 Add converters to AvroSimpleFeature setAttribute() for compatibility

Included:  Adding tests for converting empty strings to nulls;
adding validation and implementing setAttributes; adding test;
creating non-conversion setters for speed; adding explicit conversion.
GEOMESA-103 AvroSimpleFeature return nulls for attrs that don't exist

Making AvroSimpleFeature return nulls like SimpleFeatureImpl for attributes that don't exist in the feature
GEOMESA-95 SpatioTemporalIndexSchema should accept Query

* Refactored SpatioTemporalIndex* to be Index*.
* Changed IndexSchema to accept a GT Query.
GEOMESA-112 updating assembly for geoserver 2.5.x, accumulo 1.5.1, and hadoop 2.2
GEOMESA-102 filter-to-accumulo should handle ANDs and ORs

Simplistic addition that supports relativley simple
conjunction and disjunction.  Does NOT support negation.
Corrected ECQL syntax in documentation.
Extension for simplistic handling of NOT term.
Changes based on reviewer comments.
Additional changes motivated by reviewer comments.  Rebased against LT master.