sPuReMD: update QMMM interface for specifying molecular charge constraints for charge model (EEM only currently).

sPuReMD: fix issue with atoms exactly on the upper boundary of the simulation box not being correctly binned into grid cells for the cell method. Refine conversion constants for kinetic energy and temperature calculations to obtain better agreement with the Fortran ReaxFF codebase.

sPuReMD: fix code to remove several compiler warnings. Remove unused code. Disable compilation of several debug routines. Other code clean-up.

sPuReMD: add support for user-defined molecular charge constraints with EEM (using MOLCHARGE keyword in BGF geometry files). Fix issue with far neighbor list not being initialized for certain edge cases.

PG-PuReMD: implement MPI+CUDA versions of SDM, PIPECG, PIPECR for charge solver methods (along with missing dual QEq versions).

PG-PuReMD: use a warp of threads for addtional bonded interaction computations (bond orders, bonds, lone pair/over/under).

PG-PuReMD: use a warp of threads for apply bond derivatives to forces and simplify these code paths.

PG-PuReMD: fix incorrect summations in kinetic energy and temperature calculation functions. Replace several hand-coded device-wide reduction kernels with CUB libary reduction.

PG-PuReMD: split bond and hbond initialization kernels for future optimizations. Cleanup CUDA code related to far neighbor list being in full format (remove unnecessary conditionals and arithmetic).

sPuReMD: enable setting the number of OpenMP threads via control file keyword or OpenMP environment variable (OMP_NUM_THREADS).

sPuReMD: make zlib dependency optional (trajectory file compression). PG-PuReMD: remove erroneous zlib header file inclusion.

sPuReMD: fix OpenMP compilation issue with specifications prior to 4.0 (behavior change regarding implicit shared attribute assignment to const variables).

QMMM interface related: ignore QM-MM bonds while forming bond lists, update charge matrix so that the total charge constraint only applies to QM atoms