Print out all options to BenchmarkFilters

Previously, if you used the --help option, you would get VTK-m's initialize options and Google benchmark's options, but you would not get the special options for the algorithms in this benchmark. Now, all the potential options should be printed when --help is added to the command line.

The help for BenchmarkFilters now looks like this. It is a little messy, but readable.

$ BenchmarkFilters --help
Usage: BenchmarkFilters [input data options] [benchmark options]
Input data options are:
  -h, --help             Display this help.
  --device, -d <dev>                  Force device to dev. Omit device to list
                                      available devices.
  -v <#|INFO|WARNING|ERROR|FATAL|OFF> Specify a log level (when logging is
                                      enabled).

  --num-threads <N>      Specify the number of threads to use.
  --file <filename>      File (in legacy vtk format) to read as input. If not
                         specified, a wavelet source is generated.
  --point-scalars <name> Name of the point scalar field to operate on.
  --cell-scalars <name>  Name of the cell scalar field to operate on.
  --point-vectors <name> Name of the point vector field to operate on.
  --wavelet-dim <N>      The size in each dimension of the wavelet grid (if
                         generated).
  --tetra                Tetrahedralize data set before running benchmark.
benchmark [--benchmark_list_tests={true|false}]
          [--benchmark_filter=<regex>]
          [--benchmark_min_time=<min_time>]
          [--benchmark_repetitions=<num_repetitions>]
          [--benchmark_report_aggregates_only={true|false}]
          [--benchmark_display_aggregates_only={true|false}]
          [--benchmark_format=<console|json|csv>]
          [--benchmark_out=<filename>]
          [--benchmark_out_format=<json|console|csv>]
          [--benchmark_color={auto|true|false}]
          [--benchmark_counters_tabular={true|false}]
          [--v=<verbosity>]