Added countdown mode
>> added commands '/digitalclock setcountdown <clock name> <time in seconds>' and '/digitalclock disablecountdown <clock name>'
Commands '/digitalclock stopclocks' and '/digitalclock runclocks' are replaced with '/digitalclock stopclock <clock name>' and '/digitalclock runclock <clock name>'
>> multiple tasks, one task for each running clock
Added possibility of own numbers of any width and any height, defaults are the old ones, 5 blocks high and 3 blocks wide
>> you can rewrite them in settings.yml file, during to instructions on page How to use in section Setting the look for numbers
Added CountdownEndEvent thrown when some countdown ends, you can find more information on github
