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
throw new PropertyValueException( element, prop, value,
					PropertyValueException.DESIGN_EXCEPTION_VALUE_LOCKED );
		}
		
		
		if ( element.isVirtualElement( ) && element instanceof Cell )
		{
			propName = prop.getName( );
			if ( ICellModel.COL_SPAN_PROP.equalsIgnoreCase( propName )
					|| ICellModel.ROW_SPAN_PROP.equalsIgnoreCase( propName )
					|| ICellModel.DROP_PROP.equalsIgnoreCase( propName )
					|| ICellModel.COLUMN_PROP.equalsIgnoreCase( propName ) )
			{
				throw new PropertyValueException(
						element,
						prop,
						value,
						PropertyValueException.DESIGN_EXCEPTION_PROPERTY_CHANGE_FORBIDDEN );
			}
		}
		if ( element instanceof MasterPage )
		{
			
			
			
			propName = prop.getName( );
			if ( !( (MasterPage) element ).isCustomType( module )
					&& ( IMasterPageModel.WIDTH_PROP.equals( propName ) || IMasterPageModel.HEIGHT_PROP
							.equals( propName ) ) )
			{