GEOMESA-443 Test TimeSnap and GridSnap corner cases

* Adds tests for TimeSnap class.
* Adds corner case test for GridSnap and addresses a corner case.
GEOMESA-445 Create Temporal Density Iterator
GEOMESA-490 removing objenesis, vecmath, jgraphx, snappy and jline

* Had to also remove DBScan process, which relied heavily on vecmath
* Objenesis is still a test dependency
GEOMESA-498 adding filters to modify feature writer
GEOMESA-452 Accumulo Coverage Format connection parameters aren't saved in Geoserver

* Connection parameters in the datastore form are set using values parsed out from the coverage url
* Shared FORMAT between CoverageReader and CoverageStoreEditPanel