Stop Generating New Scale Levels Earlier

[cmhulbert]

The current implementation of N5ScalePyramidSpark#downsampleScalePyramid will generate scale levels that are extremely small such that that smallest scale levels potentially have only a single value along one or more dimensions.

Some ongoing conversations agreed that it was reasonable to stop sooner ( as a rule of thumb, not a hard rule), so as not to generate unnecessary scale levels. A suggestion to only downsampling until the dimensions at the highest scale level are less than 64 in all dimensions seemed reasonable.

I'd propose replacing the lines linked about with something along the lines of:

if ( Arrays.stream( downsampledDimensions ).max().getAsLong() < 64  || Arrays.stream( downsampledDimensions ).min().getAsLong() < 1 )
    break;