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 is necessary to be able to re-build a Runtime object with an new
set of "commandline arguments". For example if a test wants to test two
calls to imag, for example a "add" operation followed by a "remove" operation.
These functions are feature-gated therefor and should only be used in
tests.
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.
