Add powerpipe.io as a package

[weitzj]

Please package https://github.com/turbot/powerpipe as a package
As a reference, one can look at the steampipe package, which is already present in nixpkgs.

Currently nixpkgs contains steampipe.io as a package.

As far as I understood, steampipe is going to be split in multiple binaries, called:

steampipe (already packaged)
powerpipe
flowpipe

This ticket tracks the request to get powerpipe packages into nixpkgs.