Convert Protocol Encoder/Decoder to a declerative style

[damageboy]

Probably all messages could be converted from _enc.EncodeString(version); _enc.EncodeString(contract.Symbol); _enc.EncodeStringcontract.Exchange);

to something more declarative like: msg = new TWSProtocolMessage { { 16 }, { ctx.Contract.Symbol }, { ctx.Contract.Exchange }, };

etc.