BUGFIX: Fix Cosmo64 reader names/labels

Put Cosmo64 core reader in a different proxy group to
disambiguate it from the vtkFileSeriesReader. Also, removed
all labels. Now, the name of each property is used to also
define its label s.t. both python/C++ interfaces have the same
access patern.

git-svn-id: https://svn.alcf.anl.gov/repos/DarkUniverse/hacc/trunk/cosmotools@1452 952bdfbe-fa2e-45c0-a9ae-ac90d4a62daf
ENH: Move Extent utilities in common
DOC: Improve documentation of MPIUtilities.h
ENH: ExtentUtilities namespace pattern re-design

Change ExtentUtilities to encapsulate methods within a
namespace cosmotk::ExtentUtilities instead of being a class
object with static methods.
ENH: Compile ExtentUtilities and ExtentPartitioner
COMP: Update sfprobe/CMakeLists.txt

Update sfprobe/CMakeLists.txt s.t. ExtentUtilties and ExtentPartitioner are
no longer compiled. This functionality has been moved in common.
ENH: Update ExtentPartitioner namespace
COMP: Use cosmotk::ExtentUtilities instead
WIP: