PG-PuReMD: fix issue with some interaction lists not being initialized on first step of simulations from restarted runs. Fix typos in C++ code for utilizing C code (__cplusplus). Clean up C code for utilizing C++ code (unconditional extern's for unmangled member naming). Ensure that CUDA thread and block sizes are correctly set. Tweaks to memory transfers and allocation logic in integration code (GPU). Fix logic error with charge matrix allocation in GPU code. Other code clean-up.

PG-PuReMD: merge changes from sPuReMD and PuReMD for validation work for simulation accuracy. Small correction to lone pair energy calculation. PuReMD: code formatting changes to better align with sPuReMD. sPuReMD: fix issue with valence angle calculations not setting list indices under certain sitations (taking previous continue statement missed index assignment).

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.