PG-PuReMD: begin merging preconditioner code from sPuReMD. Make data structures between sPuReMD and PG-PuReMD consistent. Update control file parsing.

PG-PuReMD: merge memory management and step retry logic from MPI+GPU code into MPI-only code. Fix and backport numerous bugs (void pointer arithmetic and dereferences, etc.). Update code to match new data structures. Begin merging changes from OpenMP code (sPuReMD) for preconditioning work.

sPuReMD: make CoM logic consistent with PuReMD. Other build system updates for debugging and newer versions of MPICH.

All: fix issue with pi bonds being incorrectly computed in bond orders. Patch originally submitted to LAMMPS mailing list by Tomas Trnka, SCM (refer to Issue #837 on Github).

PG-PuReMD: fix error due to function prototype change. PuReMD: fix issues with GCC new inline behavior, fix reax_list bugs. sPuReMD: change exit code to zero.

PG-PuReMD: complete memory changes. Remove max register per CUDA function option in build. Other misc. changes.

PG-PuReMD: only perform device-side reductions on energy at requested update energy frequency. Fix trajectory file output. Add num. retries of main simulation loop to log file. Other refactoring.

PG-PuReMD: fix nvcc build issue where incorrect C++ compiler was utilized. Fix race condition with three body list computation. Remove debug code. Other misc. refactoring.

PG-PuReMD: begin enhancements. Enable sim. step retries. Enable far neighbors list max per atom. Other general code clean-ups.

PG-PuReMD: fix build system linker argument ordering (LDFLAGS -> LDADD). Fix inline functions. Disable optimized CUDA code generation by default (added Makefile flags to enable along with preprocessor defs to enable relevant code paths).

PG-PuReMD: fix include guards, resolve implicit function declarations, fix inline issues with GCC v5 (C99 std). Other general code clean-up.

PG-PuReMD: fix issue with hydrogen bond cutoff with systems without hydrogen atoms. Remove debugging info for MPI-only version of PG-PuReMD.

PG-PuReMD: include forgotten headers for distribution. Fix CUDA installation check. Additional updates for build system.