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
I verified they still get excluded, so it's a non-issue.