Create a message class

[joaocac]

Explanation

A message class will implement all the required functionality to deal with message-related information.
This will serve as an interface between the client and the API

Current Need

• Set/Get message content
• Get tracking information (if active)
• Set/Get envelope header (entity, channel, return address, etc...)

Future

• Encryption / Decryption so we can securely send messages (for now they can be set externally)

[joaocac]

The API should have a message factory allowing the client to worry only with the message dealing.

Eg:

// message will be a reference to an API internal message instance
let message = API.createPublicMessage('ENTITY', 'CHANNEL')
message.set(messageContent)

message.send()
// or
message.sendAndReplyTo(listener)