sPuReMD: fix small differences in valence angle energy term with Fortran ReaxFF code. Other minor code updates.

sPuReMD: change log file column headers to be contigious strings of non-whitespace characters to facilitate post-processing.

Fix build issue where config.h.in is only generated once (for sPuReMD) => common file across all versions.

sPuReMD: fix issue with incorrect cutoff being applied for periodic neighbors in small simulation boxes (nonb_cut -> vlist_cut). Other clean-up and debug I/O updates.

Build toos: refactor to remove recurisve Makefiles. Fix issue with OpenMP flags being overridden when user supplied value for CFLAGS variable.

sPuReMD: add ACKS2 geometry-dependent forces to tabulated computation of van der Waals and Coulomb terms. Replace double precision equality check with difference comparison.

sPuReMD: add missing header files when distributing (make dist). Fix OpenMP bug with ACKS2 geometry-dependent force contribution. Fix small OpenMP compilation issue. Update tools/run_sim.py to respect geo_format parameter and infer if not present for md_run_custom.

sPuReMD: default to vlist_buffer of 2.5 angstroms. Fixes to cutoffs used in far neighbor list generation.

sPuReMD: re-enable SMALL_BOX_SUPPORT. Fix issue with far nbrs list being incorrectly generated for small boxes (missing nbr ID). Fix issue with ACKS2 matrix being incorrect for small boxes due to multiple non-zeros being added for each perioidic image of an atom (accumulate instead). Add missing ACKS2-specific energy and forces term. Clean-up far nbr list estimation and generation code for small boxes. Do not add far list struct entries unless the atom is below the specified cutoff.

Build systems updates for sPuReMD, PuReMD-GPU, and PG-PuReMD (use safer optimization level defaults).

Tools: add functionality to run different code version (serial, OpenMP, MPI, MPI+GPU). Update sPuReMD control file parser to ignore non-shared memory parameters.

sPuReMD: refactoring to align code with PuReMD. Disable SMALL_BOX_SUPPORT. Refactor to remove union-based polymorphic behavior for reax_list. Other general code clean-ups.

sPuReMD: fix ILUTP bug with order of permutation matrix application. Refactor dense vector permutation code (GC, ILUTP).

sPuReMD: backport efforts for SMALL_BOX_SUPPORT from OGOLEM version of code and conditionally compile. Remove unused code. Other code clean-up.

sPuReMD: backport changes for reax_list, struct declaration/definition separation, interaction_function.

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

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

sPuReMD: add checks on string and file handling. Rewrite PDB writing to be line-by-line. Other refactoring.

sPuReMD: remove debug prints. Default to no good initial guess for out of range values for spline extrapolation.

sPuReMD: move NaN checks on system energy to after logging. This allows better diagnostics for, e.g., the potential logging.

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).

sPuReMD: separate total energy computation and fix Python driver bug with structure definition for ctypes. Allow disabling file logging during simulation.