Tools using BlockProcessor class are limited to focal neighborhood sizes <75

[noahslocum]

The block size passed to the BlockProcessor class (in utils.py) is currently determined (in depth_statistics.py) by limiting the maximum number of elements in a ndarray to 10^8 elements to avoid a Memory Error. This limits the maximum neighborhood size for IQR and Kurtosis to 73. Block size could instead be determined using an adaptive approach that evaluates the capabilities of the user's machine so that larger neighborhood sizes can be used when more memory is available.