This commit contains a "big bang" refactor/rewrite which does the
following:
- Replaces all `SCard*` FFI calls with the `pcsc` crate, which provides
a safe, portable PC/SC API across Windows, macOS, and Linux
- Refactors the `util` module into modules representing the various
device functions and concepts, e.g. `certificate`, `key`, `mgm`
- Replaces all usage of `libc` with `std` functionality, and in many
places rewriting functionality to use safe code.
- Removes `ykpiv_` from all function names, and `Piv*` from type names.
In 20/20 hindsight I wish I had done this commit more incrementally so
as to make it easier to review. Que sera sera.
However, realistically we need to test all functionality on the device
to ensure that it actually works. Going forward I would like to put
pretty much all of the current code behind an `untested` cargo feature,
and then remove it for each bit of functionality we test.
Carl Wallace