* 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