GEOMESA-418 Time-enabled layer previews are not handled optimally

* Recognizing binary inequality filters involving canonical time variable as temporal filters and handling them like before/after.
* allowing before/after and inequality operators to take named field on left or right of operator
* test verifies that < and <= are treated like BEFORE; > and >= are treated like AFTER
* moved filter typeclasses to utils module and implemented ops
* warn-logging errors on STIdxStrategy.execute rather than letting geotools eat them
* modifying temporalFilters to properly capture temporal filters with the temporal attribute on the right
GEOMESA-485 Geometries are being written to the attribute index

Filter out geometry descriptors from getSecondaryIndexedAttributes
GEOMESA-491 Add ability for Geoserver plugin to scan multiple columns

Changes plugin wms layer configurations to allow for a list of columns to scan
GEOMESA-488, 492 Understand and remove use of jai_core, CoverageReader's VersioningIterator's random name string isn't created properly

Excluded jai_core and removed usages of jai_core functionality from geomesa-plugin. Also
fixed an issue with a random name not being properly generated for VersioningIterator
in CoverageReader