This patch is a rewrite for the imag-link commandline to automatically
recognize whether an internal or an external link is about to be made
and automatically do the right thing.
The commandline got a lot easier and also smaller in size (as in number
of commands), but the functionality should remain the same.
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.
