Bug 279452 [Compatibility] Parameterized command mechanism support
Parameterized commands like showView need to be able to access their parameters (like the view ID) PW
bundles/org.eclipse.e4.ui.services/src/org/eclipse/e4/ui/internal/services/ContextHandlerService.java
private static final String PREFIX = "HDL_";
	private IEclipseContext context;
	public ContextHandlerService(IEclipseContext context) {
		this.context = context;
	}
	public void activateHandler(String commandId, Object handler) {
		context.set(PREFIX + commandId, handler);
	}
	public Object executeHandler(String commandId) {
		Object handler = context.get(commandId, new Object[] { "handler" });
		if (handler == null) {
			return null;
		}
		IContributionFactory factory = (IContributionFactory) context.get(
				"org.eclipse.e4.core.services.IContributionFactory",
				new Object[] { handler });