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
if ( element instanceof ContentElement )
		{
			if ( !( (ContentElement) element ).isLocal( ) )
			{
				ContentElementCommand attrCmd = new ContentElementCommand(
						module, element, ( (ContentElement) element )
								.getValueContainer( ) );
				attrCmd.doSetProperty( prop, value );
				return;
			}
		}
		doSetProperty( prop, value );
	}
	/**
	 * 
	 * @param prop
	 * @param value
	 * @throws SemanticException
	 */
	private void setElementTypeProperty( ElementPropertyDefn prop, Object value )
			throws SemanticException
	{
		ContainerContext context = new ContainerContext( element, prop
				.getName( ) );
		CommandStack stack = getActivityStack( );
		PropertyRecord record = new PropertyRecord( element, prop, value );
		stack.startTrans( record.getLabel( ) );
		ContentCommand cmd = new ContentCommand( module, context );
		
		List contents = context.getContents( module );