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/SimpleGroupElementHandle.java
}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.api.GroupElementHandle#isSameType()
	 */
	public boolean isSameType( )
	{
		if ( elements.size( ) == 0 )
			return false;
		IElementDefn baseDefn = null;
		for ( int i = 0; i < elements.size( ); i++ )
		{
			Object item = elements.get( i );
			if ( !( item instanceof DesignElementHandle ) )
				return false;
			IElementDefn elemDefn = ( (DesignElementHandle) item ).getDefn( );
			if ( baseDefn == null )
				baseDefn = elemDefn;
			if ( elemDefn != baseDefn )
				return false;
		}
		return true;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.api.GroupElementHandle#visiblePropertyIterator()
	 */
	public Iterator visiblePropertyIterator( )