Print big times using large time units to avoid too long labels

**Original reporter**: _MikolajKonarski_

On very large eventlogs, the labels of histogram bars overwrite each other, because the numbers (spark lengths) grow too big. Extend and use the function that prints time in different units to handle large time values with large time units, that is kiloseconds and megaseconds, or perhaps minutes, hours, days, weeks, etc.
