Add --no-timestamp; makes timestamps optional but default on

[gominoa]

trafficstars

Also hash rate display looks cool with rolling timestamp

Deepbit 09/07/2011 03:55:29 [184.868 MH/s (~390 MH/s)] [Rej: 0/1 (0%)]

[gominoa]

I prefer without timestamp as I log to file with --quiet and --verbose and my logger adds timestamp anyway. But rolling timestamp with hash rate looks sweet and most people probably dont log to file.