run nb in separate window

[mwermelinger]

A tutor wrote:

The Jupyter server is running in the background, but it writes all its log messages to the PowerShell window, making the Powershell pretty unusable. I think it makes much more sense to launch a separate window than trying to have two processes share the same one. I've experimented with removing the -NoNewWindow directive from the nb function in install.ps1 and I think it looks better.

While this sounds sensible and is easy to implement for Windows (although the instructions would have to be updated), I prefer to postpone this for 24J to avoid a divergence between Windows and Unix and between students who install now (the VLE already opened) those who install later.