Editing doc/notes/ddMd
Optimization of zero forces functions.
Improvements to timing statistics output.
Adding CellAtom, caching of position and id.
Small optimization of PairList (for 1 atom in cell)
Optimizing pairlist.
Improved timing outputs, fixed overflow bug.
Editing documentation in Exchanger.cpp
Merge branch 'devel' of github.com:/dmorse/simpatico into devel
Merge branch 'devel' of github.com:/dmorse/simpatico into devel

Conflicts:
	doc/notes/ddMd/AtomSort
Reordering includes to put mpi.h before stdio.h.

These changes were required to get the code to compile on
the intel compiler with the intel MPI library, and are the
result of a name clash between the C++ MPI standard and
the C++ standard library.
Fixing makefile for ChainMaker tool.