Rewrite translated code to use the pcsc crate

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.

src/lib.rs

@@ -9,6 +9,9 @@
 //! utilize PIV encryption and signing keys which can be generated, imported,
 //! and stored on YubiKey devices.
 //!
+//! See [Yubico's guide to PIV-enabled YubiKeys][6] for more information
+//! on which devices support PIV and the available functionality.
+//!
 //! Supported algorithms:
 //!
 //! - **Authentication**: `3DES`
@@ -24,23 +27,24 @@
 //!
 //! ## History
 //!
-//! This library is a Rust translation of the [yubico-piv-tool][6] utility by
+//! This library is a Rust translation of the [yubico-piv-tool][7] utility by
 //! Yubico, which was originally written in C. It was mechanically translated
-//! from C into Rust using [Corrode][7], and then subsequently heavily
+//! from C into Rust using [Corrode][8], and then subsequently heavily
 //! refactored into safer, more idiomatic Rust.
 //!
 //! For more information on `yubico-piv-tool` and background information on how
 //! the YubiKey implementation of PIV works in general, see the
-//! [Yubico PIV Tool Command Line Guide][8].
+//! [Yubico PIV Tool Command Line Guide][9].
 //!
 //! [1]: https://www.yubico.com/products/yubikey-hardware/
 //! [2]: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-73-4.pdf
 //! [3]: https://www.yubico.com/
 //! [4]: https://en.wikipedia.org/wiki/CCID_(protocol)
 //! [5]: https://www.nist.gov/
-//! [6]: https://github.com/Yubico/yubico-piv-tool/
-//! [7]: https://github.com/jameysharp/corrode
-//! [8]: https://www.yubico.com/wp-content/uploads/2016/05/Yubico_PIV_Tool_Command_Line_Guide_en.pdf
+//! [6]: https://developers.yubico.com/PIV/Introduction/YubiKey_and_PIV.html
+//! [7]: https://github.com/Yubico/yubico-piv-tool/
+//! [8]: https://github.com/jameysharp/corrode
+//! [9]: https://www.yubico.com/wp-content/uploads/2016/05/Yubico_PIV_Tool_Command_Line_Guide_en.pdf
 
 // Adapted from yubico-piv-tool:
 // <https://github.com/Yubico/yubico-piv-tool/>
@@ -86,10 +90,31 @@
 )]
 
 mod apdu;
+pub mod cccid;
+pub mod certificate;
+pub mod chuid;
+pub mod config;
 pub mod consts;
+pub mod container;
 pub mod error;
-mod internal;
-pub mod util;
+pub mod key;
+mod metadata;
+pub mod mgm;
+pub mod msroots;
+mod response;
+mod serialization;
+pub mod settings;
+mod transaction;
 pub mod yubikey;
 
-pub use self::yubikey::YubiKey;
+pub use self::{key::Key, mgm::MgmKey, yubikey::YubiKey};
+
+/// Algorithm identifiers
+// TODO(tarcieri): make this an enum
+pub type AlgorithmId = u8;
+
+/// Object identifiers
+pub type ObjectId = u32;
+
+/// Buffer type (self-zeroizing byte vector)
+pub(crate) type Buffer = zeroize::Zeroizing<Vec<u8>>;