Add tutorial to main

[tkoskela]

To make the tutorial materials more accessible, let's add them to main. There should be no functional changes to the code, except adding stream to benchmarks/examples and I think it's an useful example.

@ilectra please check that the post-processing files merge ok

[ilectra]

I'm done with adding/checking the postprocessing stuff. Once we update the notes to final version, feel free to merge. I'll run the whole tutorial on archer2 tomorrow, just in case...

[ilectra]

@tkoskela I'm done updating the files needed for the post-processing part of the tutorial, as well as the tutorial.md in your hackmd. AFAIC, you can merge this once you bring the newest tutorial.md over.