Bug 123406 Add geLocaltStringProperty in GroupElementHandle and GroupPropertyHandle
Please refer to 123405. GUI need a way to get the local setting of given property because current getStringPropery method will return inherited value if there are no local value.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/GroupPropertyHandle.java
assert handle instanceof SimpleGroupElementHandle;
		this.handle = handle;
		this.propDefn = propDefn;
	}
	/**
	 * Indicates whether the group of element share the same value for this
	 * property.
	 * <p>
	 * If all element has a <code>null</code> value for this property, it is
	 * considered that they share the same value.
	 * 
	 * @return <code>true</code> if the group of element share the same value.
	 */
	public final boolean shareSameValue( )
	{
		Iterator iter = handle.getElements( ).iterator( );
		
		if ( !iter.hasNext( ) )
			return false;
		DesignElementHandle elemHandle = (DesignElementHandle) iter.next( );
		
		String baseValue = elemHandle.getStringProperty( propDefn.getName( ) );
		while ( iter.hasNext( ) )
		{
			elemHandle = (DesignElementHandle) iter.next( );
			String value = elemHandle.getStringProperty( propDefn.getName( ) );
			if ( baseValue == null )
			{
				if ( value != null )
					return false;