Use ai3/go-common for password hashing

server/authserver.go

server/authserver_test.go

vendor/git.autistici.org/ai3/go-common/pwhash/password.go

vendor/github.com/amoghe/go-crypt/LICENSE

vendor/github.com/amoghe/go-crypt/README.md

vendor/github.com/amoghe/go-crypt/crypt.go

vendor/github.com/amoghe/go-crypt/crypt_r.go

vendor/github.com/amoghe/go-crypt/version.go

vendor/golang.org/x/crypto/argon2/argon2.go

vendor/golang.org/x/crypto/argon2/blake2b.go

vendor/golang.org/x/crypto/argon2/blamka_amd64.go

vendor/golang.org/x/crypto/argon2/blamka_amd64.s

vendor/golang.org/x/crypto/argon2/blamka_generic.go

vendor/golang.org/x/crypto/argon2/blamka_ref.go

vendor/golang.org/x/crypto/blake2b/blake2b.go

vendor/golang.org/x/crypto/blake2b/blake2bAVX2_amd64.go

vendor/golang.org/x/crypto/blake2b/blake2bAVX2_amd64.s

vendor/golang.org/x/crypto/blake2b/blake2b_amd64.go

vendor/golang.org/x/crypto/blake2b/blake2b_amd64.s

vendor/golang.org/x/crypto/blake2b/blake2b_generic.go