Initialize should have --help with AddHelp option

When you give Initialize the AddHelp option, it adds command line arguments -h and --vtkm-help that will print out a usage statement and exist. That's weird because users will expect --help. Providing -h but not --help does not make sense.

Instead, if AddHelp is active, then it should provide the --help and --h. It should probably also add --vtkm-help for completeness. If AddHelp is not active, then just --vtkm-help should be added. This should be a safe way to allow users to query VTK-m args even if the application does not provide the VTK-m option help.