GEOMESA-159 Eliminate redundant copies of a value in the SimpleFeatureFilteringIterator
GEOMESA-288 Export to stdOut

Exporting to stdOut is now achievable by giving the export command the -s or --stdout flag. Additionally, the list and describe commands now have a -q or --quiet option for better piping of their outputs.
GEOMESA-278 removing unused action page
GEOMESA-291 adding more data store params to GeoServer interface
GEOMESA-268 updating menu icons in geoserver
GEOMESA-280 fixing NPE for non-existing props
GEOMESA-298 Implement DBSCAN as a WPS
GEOMESA-302 Export overwrites files without prompting

Exported files are now guaranteed to have a unique filename through using File.createTempFile,
which appends a unique id to each file name. The current DateTime is also appended
to make it easier to identify exported files.
switching file name uniqueness based on comments
updating README and warning message on delete
fixing geomesa shell wrapper