WhichBin determines which bin "value" is in given a list of bin centers and bin sizes. If value not in any bin, -1 returned. This allows for non-contiguous bins and nonuniformly spaced bins.

WhichBin determines which uniform bin "value" is in. If data is beyond last bin, the last bin is returned. If the data is smaller than first bin, the first bin is returned. This assumes bins are contiguous.