Create a dedicated crate for the DKG (#141)

* Add dkg crate

* Remove F_len and G_len

They're generally no longer used.

* Replace hash_to_vec with a provided method around associated type H: Digest

Part of trying to minimize this trait so it can be moved elsewhere. Vec, 
which isn't std, may have been a blocker.

* Encrypt secret shares within the FROST library

Reduces requirements on callers in order to be correct.

* Update usage of Zeroize within FROST

* Inline functions in key_gen

There was no reason to have them separated as they were. sign probably 
has the same statement available, yet that isn't the focus right now.

* Add a ciphersuite package which provides hash_to_F

* Set the Ciphersuite version to something valid

* Have ed448 export Scalar/FieldElement/Point at the top level

* Move FROST over to Ciphersuite

* Correct usage of ff in ciphersuite

* Correct documentation handling

* Move Schnorr signatures to their own crate

* Remove unused feature from schnorr

* Fix Schnorr tests

* Split DKG into a separate crate

* Add serialize to Commitments and SecretShare

Helper for buf = vec![]; .write(buf).unwrap(); buf

* Move FROST over to the new dkg crate

* Update Monero lib to latest FROST

* Correct ethereum's usage of features

* Add serialize to GeneratorProof

* Add serialize helper function to FROST

* Rename AddendumSerialize to WriteAddendum

* Update processor

* Slight fix to processor

crypto/dkg/README.md

@@ -0,0 +1,12 @@
+# Distributed Key Generation
+
+A collection of implementations of various distributed key generation protocols.
+
+All included protocols resolve into the provided `Threshold` types, intended to
+enable their modularity.
+
+Additional utilities around them, such as promotion from one generator to
+another, are also provided.
+
+Currently included is the two-round protocol from the
+[FROST paper](https://eprint.iacr.org/2020/852).