Bug 176450 Support link to CSS Feature(Model Part)
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/ReferenceableElement.java
* @param propName
	 *            the property name.
	 */
	public void addClient( DesignElement client, String propName )
	{
		clients.add( new BackRef( client, propName ) );
	}
	/**
	 * Drops a client. Should be called only from
	 * {@link DesignElement#setProperty( ElementPropertyDefn, Object )}.
	 * 
	 * @param client
	 *            The client to drop.
	 */
	public void dropClient( DesignElement client )
	{
		dropClient( client, null );
	}
	/**
	 * Drops a client.
	 * 
	 * @param client
	 *            The client to drop.
	 * @param propName
	 *            the property name
	 */
	public void dropClient( DesignElement client, String propName )
	{
		for ( int i = 0; i < clients.size( ); i++ )
		{