Bug 146761 All structure properties change can't be restore
Steps to reproduce: 1.New a report, extends lib.table 2.Add a structure property(such as filter, column binding...) on table 3.Choose the table, click "Restore Property" Expected result: Local propery is removed Actual result: Local property can't be removed so that "Restore Property" is always enabled
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/GroupPropertyHandle.java
elemHandle.setProperty( propDefn.getName( ), value );
			}
		}
		catch ( SemanticException e )
		{
			actStack.rollback( );
			throw e;
		}
		actStack.commit( );
	}
	/**
	 * Set the string value on a group of elements. This operation will be
	 * executed within a transaction, it will be rollbacked if any set operation
	 * failed.
	 * 
	 * @param value
	 *            the string value to set
	 * @throws SemanticException
	 *             if the property is undefined on an element or the string
	 *             value is invalid.
	 * @see SimpleValueHandle#setStringValue(String)
	 */
	public void setStringValue( String value ) throws SemanticException
	{
		setValue( value );
	}
	/**
	 * Return the property definition.
	 * 
	 * @return the property definition.