Fixed SpCell::getNeighbors & SpCellList class. Added unit tests.

Added unit tests for SpCell and SpCellList classes based of the unit tests
for Cell and CellList classes in ddMd/neighbor.  Changed the way offsets
are calculated for finding neighboring cells based on a hybrid of the way
the grid and McMd::CellList calculate neighbors to take boundary conditions
into account.  Some unit tests need to be fixed and more need to be added
to test the SpCell::getNeighbors function.
Added SpCellList unit tests and fixed getNeighbors

I fixed ealier unit tests where the grid was too small by adjusting
the cutoff distance.  I also added a unit test for SpCell::getNeighbors
based off of the test from ddMd::cell::getNeighbors.  After looking
running this test, it was clear that getNeighbors was double counting
pairs.  This was fixed by only returning atoms from cells with cellIds >=
this->id_.
accidentally left this here
Added SpCell destructor to free up memory allocated for OffsetArray

When SpCellList::makeGrid is called, memory is allocated to store
the offsets needed to calculate the neighbors.  This memory should be
freed if the SpCell object is later destroyed.
Compile with Debugging Symbols when UTIL_DEBUG is enabled

Changed the build system slightly to compile with no optimizations
and and include debugging symbols when UTIL_DEBUG is enabled.  These
options are the same whether you're compiling with gcc or intel icc.
Also fixed a small one-line compile error from previous commits.
Fixed Memory Leak
Merge branch 'sp' of https://github.com/polymer1/simpatico into polymer1-sp

Conflicts:
	src/ddMd/sp/neighbor/SpCell.cpp
	src/ddMd/sp/neighbor/SpCell.h
	src/ddMd/sp/neighbor/SpCellList.cpp
	src/ddMd/sp/neighbor/SpCellList.h