Execution example::

  select Entries --output_columns 'highlight_full("Groonga is very fast fulltext search engine.", "NormalizerAuto", true, "Groonga", "<span class=\\"keyword1\\">", "</span>", "mysql", "<span class=\\"keyword2\\">", "</span>")' --command_version 2 --match_columns body --query "groonga"
  # [
  #   [
  #     0, 
  #     1337566253.89858, 
  #     0.000355720520019531
  #   ], 
  #   [
  #     [
  #       [
  #         1
  #       ], 
  #       [
  #         [
  #           "highlight_full", 
  #           null
  #         ]
  #       ], 
  #       [
  #         "<span class=\"keyword1\">Groonga</span> is very fast fulltext search engine."
  #       ]
  #     ]
  #   ]
  # ]
