Placed adjusting the histogram to a method.

Moved the code for adjusting the final cluster size histogram as well as
outputting it to a file to a separate method.

The histogram is not computed yet.
Size histogram works on <= 2 processors.

Cluster size histogram seems to be correct when run on 1 or 2 processors.
At least on a couple of dummy pictures. When run on 4 procs the histogram
is incorrect, it is adjusted incorrectly.