SMP client library (#9)

* functions to send SMP commands and receive responses

* refactor agent: use SMPClient

* fix tests, remove ServerClient.hs

* refactor processCommand

* fix Agent.hs

* fix SMPClient, tests

* "forever" to SMPClient process

src/Simplex/Messaging/Server/Transmission.hs

@@ -153,6 +153,8 @@ instance IsString CorrId where
 
 type PublicKey = Encoded
 
+type PrivateKey = Encoded
+
 type Signature = Encoded
 
 type RecipientKey = PublicKey