Add option to round / scale YAxis intervals to "nice numbers"

[jns-codeworks]

Add option to round YAxis intervals / ticks to nice numbers, i.e. 1,2,5 and all power-of-ten multiples of these numbers, like in this stackoverflow thread.

Standard intervals:

Nice number intervals:

[thsaravana]

This makes sense. I will try to push this in the upcoming version.