Bug 146481 Name is not necessary for extended element
Steps to reproduce: 1.New a label named "label" in library 2.New a report, extend lib.label Expected result: No name for the extended label Actual result: "label" is added as the name of label in report. It's not reasonable because "Restore Properties" is enabled even without properties change.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/GroupElementHandle.java
* Returns an iterator over the common properties that are visible. Contents
	 * of the iterator are handles to the common properties, type of them is
	 * <code>GroupPropertyHandle</code>. Note: remove is not support for the
	 * iterator.
	 * 
	 * @return an iterator over the common properties. Contents of the iterator
	 *         are handles to the common properties, type of them is
	 *         <code>GroupPropertyHandle</code>
	 */
	abstract public Iterator visiblePropertyIterator( );
	/**
	 * Checks whether a property is visible in the property sheet. The visible
	 * property is visible in all <code>elements</code>.
	 * 
	 * @param propName
	 *            the property name
	 * @return <code>true</code> if it is visible. Otherwise
	 *         <code>false</code>.
	 */
	abstract protected boolean isPropertyVisible( String propName );
	/**
	 * Clears values of all common properties(except the extends property) for
	 * the given collection of elements. Clearing a property removes any value
	 * set for the property on this element. After this, the element will now
	 * inherit the property from its parent element, style, or from the default
	 * value for the property.
	 * 
	 * @throws SemanticException
	 *             if the property is not defined on this element
	 */