IPythonVertical support

I have added an `IPythonVertical` command as I couldn't find an easy way to create vertical ipython panes (I realized when I first run `ScreenShellVertical` and close it afterwards with `ScreenQuit` and then start ipython with `IPython` it opens up in vertical but I'm not sure if that's intended or not). We can add something to the documentation if you decide to include.