ENH: Unified build for hacc

This commit adds functionality for building
genericio, cosmotools and nbody as a single
code.

From: George Zagaris <george.zagaris@kitware.com>

git-svn-id: https://svn.alcf.anl.gov/repos/DarkUniverse/hacc/trunk/cosmotools@1703 952bdfbe-fa2e-45c0-a9ae-ac90d4a62daf
Merge branch 'svn/trunk'