.ipynb download has the suffix .ipynb.txt and pdf will redirect to printer

[unkcpz]

I try to download the .ipynb and run it in the aiidalab jupyter server. There are several issues we may need to fix.

1. .ipynb download has the suffix .ipynb.txt and pdf will redirect to the printer
2. Instead of clicking to download and upload to jupyter server, we can provide wget command with links so the user can run the command and start running the notebook.

If you agree @chrisjsewell @mbercx, I can managing to add the wget command with links. But I don't know how to fix the filename suffix issue.