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
else if ( item instanceof DesignElementHandle )
					{
						cmd.add( ( (DesignElementHandle) item ).getElement( ) );
					}
				}
			}
		}
		catch ( SemanticException e )
		{
			stack.rollback( );
			throw e;
		}
		stack.commit( );
	}
	/**
	 * Remove template definition from module if the definition is no longer
	 * refferenced when setting
	 * <code>IDesignElementModel.REF_TEMPLATE_PARAMETER_PROP</code> null.
	 * 
	 * @param prop
	 *            should be
	 *            <code>IDesignElementModel.REF_TEMPLATE_PARAMETER_PROP</code>.
	 * @param value
	 *            should be null;
	 * @throws SemanticException
	 *             if any semantic exception is thrown.
	 */
	private void clearRefTemplateParameterProp( ElementPropertyDefn prop,
			Object value ) throws SemanticException
	{