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
* @param propName
	 *            name of the property.
	 * @return <code>true</code> if the group of element share the same value.
	 *         Return <code>false</code> if the property is not a common
	 *         property or elements have different values for this property.
	 */
	public final boolean shareSameValue( String propName )
	{
		GroupPropertyHandle propHandle = getPropertyHandle( propName );
		if ( propHandle == null )
			return false;
		return propHandle.shareSameValue( );
	}
	/**
	 * Set the value of a property on the given collection of elements. If the
	 * property provided is not a common property then this method simply
	 * return; Otherwise, the value will be set on the group of elements.
	 * 
	 * @param propName
	 *            name of the property.
	 * @param value
	 *            value needs to set.
	 * @throws SemanticException
	 *             if the value is invalid for the property, or the property is
	 *             undefined on the elements.
	 * @see GroupPropertyHandle#setValue(Object)
	 */
	public final void setProperty( String propName, Object value )
			throws SemanticException
	{