When a layer group is hidden, the layers in the group should all be hidden.

Paint.NET does not have layer grouping, so the PSDPlugin flattens out the layer hierarchy. Layers are treated as independent, causing layers in a hidden layer group to be visible if their visibility is set to true. This should not be the case -- the invisibility of the layer group should be applied to all of the layers within it.

Screenshot is attached. The PSD file is the one in work item 7970.