timestamp should be taken on sender device #1

Currently, when receiving a message, the current timestamp is taken to mark the message. This works pretty well, until you refresh the page. Now, all the messages have basically the same timestamp because the server re-sends all the messages. The fix is to add the timestamp to the messages.

There is also the option of getting the timestamp on the server. This means the clients are not able to modify the frontend to remove the timestamps if the room has it on. Unsure if this is wanted or not yet.

Also, add an option to a room to have timestamps or not. This is tracked in #2