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.
ok. would be nicer without the random string... could you do something like (pseudo-code):
var ouputPath: File = null
do {
  if (ouputPath == null) { Thead.sleep(1) }
  outputPath = new File(s"${load.table}_${load.name}_${DateTime.now()}", new File(s"${System.getProperty("user.dir")}"))
} while (outputPath.exists)