App.transaction ignores Layer.isVisible

If you set the `isVisible` property on a Layer inside a transaction, and then call `app.undo()`, the visibility change is not reverted.

Example code:

```
local function revealLayers(layers)
for i, layer in ipairs(layers) do
layer.isVisible = true
if layer.isGroup then
revealLayers(layer.layers)
end
end
end

app.transaction(function()
revealLayers(app.activeSprite.layers)
end)
app.undo() -- This has no effect.
```

Other actions that act directly on properties *are* reverted (I tested setting `Layer.color` instead of `Layer.isVisible`, for instance).

I suspect this is intentional in that it is consistent with the UI behavior; changing a layer's visibility doesn't seem to be revertable via Edit -> Undo. However, in a scripting context it would be useful to have a revertable visibility change. So if the behavior is intentional, this could be considered a feature request for something like `Sprite:setVisibility(visibility, revertable=false)`, where setting the second parameter to `true` adds the visibility change to the edit history.