@Override
		protected void options() {
			super.options();
			this.containerGroupsOption = option(asList("container-groups", "g"), "Container groups").withOptionalArg();
		}
A custom {@link YarnClusterCreateCommand} adding option for defining
a groups for XD's containers.

@author Janne Valkealahti
spring-xd-yarn/spring-xd-yarn-client/src/main/java/org/springframework/xd/yarn/XdYarnClusterCreateCommand.java