datalog

See #1029

The hitchhiker-tree has recently gained garbage collection support, but this still needs to be added to Datahike.

replikativ/hitchhiker-tree#16

Adding it requires to do a mark phase on all the indices of the database and then add all DB metadata keys before running the konserve sweep! phase.

I am very curious about experience of newcomers with the tutorial. I am sure it can be improved to make onboarding easier.

At some point we should probably upgrade the argument parser to use nom version 5. They got rid of most of the macro magic. I am not familiar with nom (although interested), but there is an upgrade guide that should hopefully make the transition a bit more smooth: https://github.com/Geal/nom/blob/master/doc/upgrading_to_nom_5.md

We should probably run go generate and other commands that generate code, such as goa gen, as part of our autobuilder.

An inspect stage logging either actual tuples or number of tuples flowing through a given plan stage.