Better late than never

Handbook release matching the release of DataLad v0.17.0, which was for the most part only an internal change to a different testing framework (pytest instead of nose), and thus delayed on the handbook side.

It includes contributions the new contributors @Arshitha, @ajveltri22, @complexbrains, @jkosciessa, @candleindark, and @asmacdo, as well as contributions from established contributors @mslw, @sappelhoff, @kimsin98, @adswa, @yarikoptic.

Thank you to everyone contributing ❤️