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.