capture.cpp: improve calculateTimeToNightTime
capture.cpp: improve calculateTimeToNightTime

sunwait only returns hours and minutes, not seconds, so the average actual time is 30 seconds off.  Compensate for that by getting the current seconds.
Renamed some variables for clarity of purpose.
Print a more useful log message when sleeping while waiting for nighttime.
thomasjacquin/allsky,thomasjacquin/allsky,thomasjacquin/allsky