* inventory of error handling problems and types
* Change SMP protocol errors syntax
* connection errors in agent protocol (ERR CONN), STORE error -> AGENT error
* include exception in SEInternal error
* add MESSAGE errors, remove CRYPTO and SIZE errors
* agent protocol SYNTAX and AGENT errors
* BROKER errors
* group all client command (and agent response) errors
* BROKER TRANSPORT error
* simplify Client
* clean up
* transport errors
* simplify client
* parse / serialize agent errors
* differentiate crypto errors
* update errors.md
* make agent and SMP protocol errors consistent, simplify
* update doc
* test: parse / serialize protocol errors with QuickCheck
* add String to internal error
* exponential back-off when retrying to send HELLO
* refactor Client.hs
* replace fold with recursion in startTCPClient
* fail test if server did not start, refactor
* test: wait till TCP server stops
* test: refactor waiting for server to stop
* test: fail with error if server did not start/stop
* key encoding primitives (WIP)
* use X509/PKCS8 to read/write server key files
* make PrivateKey type class
* clean up
* remove separate public key file
* specific import
* transport encryption (WIP - using fixed key, parsing/serialization works, SMP tests fail)
* transport encryption
* transport encryption: separate keys to receive and to send, counter-based IVs
* docs: update transport encryption and handshake
* transport encryption handshake (TODO: validate key hash, welcome block, move keys to system environment)
* change KeyHash type to newtype of Digest SHA256
* transport encryption: validate public key hash
* send and receive welcome block with SMP version
* refactor: parsing SMPServer
* remove unused function
* verify that client version is compatible with server version (major version is not smaller)
* update (fix) SMP server tests
* generate key pair
* crypto: sign/verify functions
* remove extension
* parse/serialize keys
* use RSA recipient/sender keys (TODO sign/verify)
* make PublicKey newtype, assign 0s to private_p & private_q
* replace SMP command parsing with Attoparsec
* rename types: Signed->Transmission, Transmission->SignedTransmission
* sign and verify commands (server tests skipped, agent tests pass)
* SMP client: avoid seralizing transmission twice when sending commands
* update SMP server tests to use command signatures
* remove support for "SEND :msg" syntax from SMP server protocol
* rename RSA module name to R to avoid confusion with C used for S.M.Crypto
* update key sizes to use bits `div` 8
* tidy up
