Adds a new custom command to Softimage.
Each command must have a unique name, so this call will fail if the name has already been registered. To avoid
this sort of conflict, you should call XSIApplication.RemoveCommand to remove any previous
registered commands, and you should try to pick names that are unlikely to be used by Softimage itself or other plug-in
developers.
Once registered, the command becomes available to scripting, and it can be attached to buttons on custom toolbars
or added to Softimage Menus.
Note: The recommended way to create custom commands is to define them as part of a self-installed plug-in. See
PluginRegistrar.RegisterCommand.