OS "Binding" -> improved Windows desktop access

* The OperatingSystem class now creates a "Binding" depending on the OS
used, which allows for accessing native things better.
* Based on the above, Windows desktop access was improved to (1) be more
reliable by asking the system itself instead of guessing and (2) include
the public (all users) desktop.
* Due to the latter, a few icons were partially out of my screen, so I
adjusted the dimensions a bit (it would be embarrassing if Jesk required
more space than the standard desktop).