Add option for higher resolution timestamp

[eHammarstrom]

Configuration setting for enabling HH:MM:SS for each irc message.

[osa1]

Should not be too hard to implement, just make sure to make it opt-in and add a configuration variable for it.

[osa1]

@eHammarstrom you can do this now if you add this line to your config:

timestamp_format: '%H:%M:%S'

[osa1]

Re-opening this as the patch was buggy and reverted.

[osa1]

Now that we have a good way to test the TUI we should give another try at this.