Using generic downloader script for Windows

[joergi]

same as #39 but for Windows

• use it for books
• use it for regular issues

[joergi]

@Jaykul - if you wanna have a look... feel free to assign yourself

the issues in the Downloader are here:

joergi/downloader#1
joergi/downloader#3

[joergi]

The script is now used to download the windows books.
maybe the regular issues can use it too!