Improve API to pass more data.

[ear1grey]

There are several reasons why passing more data per message would be useful.

1. The request for nicknames (Allow nickname support #14)- the Nick should not be part of the message content.
2. Adding message timestamps (Messages have a built in timestamp displayed next to them #16).
3. Messages now have DB ids which could be used in recognising when a message is already displayed on screen and thus does not need to be added (reducing the tendency of the UI to jump when auto-refreshed).

[ear1grey]

NB: This is a breaking change, so a new API endpoint should be used.