Bug 197589 Need constant for automaic attribute name "DateTime"
Currently when set dateTimeLevelType for cube level, model will automatically create a built-in attribute "DateTime". But the name is hard-coded. We need a public constant for this name to allow UI to access it.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/PropertyCommand.java
checkAllowedOperation( );
		assert prop != null;
		assert IDesignElementModel.REF_TEMPLATE_PARAMETER_PROP.equals( prop
				.getName( ) );
		ActivityStack stack = module.getActivityStack( );
		stack.startTrans( );
		try
		{
			ElementRefValue templateParam = (ElementRefValue) element
					.getProperty( module, prop );
			TemplateParameterDefinition definition = (TemplateParameterDefinition) templateParam
					.getElement( );
			doSetProperty( prop, value );
			if ( definition != null && !definition.hasReferences( ) )
			{
				ContentCommand cmd = new ContentCommand( definition.getRoot( ),
						definition.getContainerInfo( ) );
				cmd.remove( definition );
			}
		}
		catch ( SemanticException e )
		{
			stack.rollback( );
			throw e;
		}
		stack.commit( );
	}
	/**
	 * Private method to set property.
	 *