Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
* himalaya: add soywod to maintainers
* himalaya: make the config safer
Also added two services and more tests.
* himalaya: fix doc + typos
* himalaya: use freeform
* himalaya: run ./format
* himalaya: make use of mkPackageOption
