sPuReMD: rework charge solver for QMMM to not require explicit masking (MM atom fixed charges are not respected). Other code clean-up.

sPuReMD: ensure reallocation for multi-simulation runs happens correctly for the charge solver codepath.

sPuReMD: ensure matrix reallocation correctly occurs in multiple simulation cases where the linear system size increases.

sPuReMD: add dummy atom support for other geometry file formats (PDB, custom). Rework interal logging during debugging for memory management. Other code clean-up.

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: fix warnings (and errors) from several uninitialized memory regions due to multiple stream change. Fix race condition with valence angle computation due to mistake with dynamic shared memory. Add control file parameter for setting the number of CUDA streams. Other code clean-up.

PG-PuReMD: fix issue with post-processing step with QEq pseudo-charges (too little storage in q array). Fix issue with device-wide CUB reductions and prefix sums reallocating device memory too frequently. Rework CUDA-aware MPI code to fix issues (still seeing out-of-memory errors on Ascent cluster at OLCF).

PG-PuReMD: ensure MPI pack/unpack CUDA kernels are run in the correct stream. Other changes to bring the CUDA-aware MPI functions for the charge solver in line with their MPI counterparts.

PG-PuReMD: utlize multiple CUDA streams to run independent kernels in the ReaxFF+QEq task dependency graph.

PG-PuReMD: fix stream issue with cudaMemset's happening in default stream (switch to cudaMemsetAsync). Rework memory management in light of this change.

WIP: finish the explicit single stream port by using cudaMemcpyAsync and cudaStreamSynchronize calls.

WIP: changes to support multiple CUDA streams. This commit contains porting of all kernels from the default stream to a single non-default stream. This commit has bugs regarding cudaMemcpy's still being in the default stream (and synchronous).