add a full timestamp with date to the chat

[tooomm]

Right now there are just times which lead to confusions because you can't really tell how old messages are and days get easily mixed up:

[arxanas]

The best UI is perhaps to add a horizontal rule with the date before each section of messages for a given day. Adding the full timestamp to each line would take up a lot of horizontal space.

[tooomm]

I re-opened this on the new active repo: dr4fters/dr4ft#721