Remove FROST code. We could try to keep the public API and use the FROST code in https://github.com/ZcashFoundation/reddsa/pull/33 but that might be too much work, so I'll wait on a decision on that. Alternatively we could move the non-generic API from the PR to this repo (i.e. just define the ciphersuite in reddsa, and define the non-generic sign, aggregate etc. functions in this repo)
Closes https://github.com/ZcashFoundation/frost/issues/39
reddsacrate and delete duplicated codereddsa, and define the non-genericsign,aggregateetc. functions in this repo)