Add configurable option to disable display of 1/10 seconds

[asquared]

Occasionally, scoreboard data feeds do not provide data to within 1/10 second during the last minute of play. This is a problem, because the on-screen scoreboard always displays the tenths even if they are not counting. Interpolating from the clock feed might be possible but will be a lot of work and might result in glitches if the scoreboard doesn't give us a run/stop flag. Adding an option to just disable the display should work well and be easy to implement.