This merge solved a _LOT_ of conflicts and was a rather complicated one,
as parts of the conflict-resolution involved rewriting of half the
stuff.
This merge commit fixes all the things so a `cargo check --all`
succeeds, but I did not yet check whether tests run without failure.
This is the first part of a series of patches that reimplements the
logging backend to be more powerful and configurable.
This first patch adds types and infrastructure to be able to implement a
powerful logging abstraction.
It does not implement much functionality, except for a check whether a
module is enabled or not when logging (if configured in the config
file).
This patch removes unused crate imports reported by newer rust versions.
Some crates were only required for tests, some only for tests with
macro_import - these things were fixed with feature gates.
