adding python cmd line utility to generate ranges of problem configurations that pass a test with mpi_decomp2 and list all working 3D decompositions

updated decomp.py for python3, mostly getting rid of xrange and cast returns of map, filter, set to lists; commiting a py2 copy for reference; main command line tools seem to work in py3

modified physical box size scaling relation to reflect CORAL guidelines; minor modification to grid memory footprint calculation

added command line utility to verify that CheckDecomposition output looks ok; could have caught previous bugs, looks ok now

added command line utility that will use CheckDecomposition from SWFFT to see which decompositions the current decomposition.c code heuristics will find working pencils for

fixed bug in enumeratePencils which kept some valid pencils from being printed; other functions correctly identified when valid pencils were present so only bug at last step of printing

moving newer FFT decomposition python code to its own package, module, namespace, whatever; will add command line wrappers and README