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
GroupPropertyHandle propHandle = getPropertyHandle( propName );
		if ( propHandle == null )
			return;
		propHandle.setValue( value );
	}
	/**
	 * Clears the value of a property on the given collection of elements if the
	 * property is a common property shared by each element. 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.
	 * <p>
	 * If the property provided is not a common property then this method simply
	 * return, else, the value will be cleared on the group of elements.
	 * 
	 * @param propName
	 *            the name of the property to clear.
	 * @throws SemanticException
	 *             if the property is not defined on this element
	 */
	public final void clearProperty( String propName ) throws SemanticException
	{
		setProperty( propName, null );
	}
	/**
	 * Set the value of a property to a string . If the property provided is not
	 * a common property then this method simply return; Else, the string value
	 * will be set on the group of element.
	 * 
	 * @param propName