sPuReMD: standardize QM/MM interface. Add test codes for QM/MM interface for AVE dataset in Python and Fortran.

sPuReMD: merge changes from branch 'new_setup'. Rework interface for geometry initialization without file I/O. Other code clean-up.

sPuReMD: fix BGF parser to correctly remap atom coordinates to internal simulation box boundaries. Fix reax_list to handle case when total interactions is zero instead of terminating program.

sPuReMD: rework Fortran F90 interfaces for Amber specifics and declare this interface for such usage.

sPuReMD: fix Coulomb energy calculations for QM/MM mode. Indicate QEq model not supported with QM/MM mode. Add Fortran interface for QM/MM mode.

sPuReMD: add QMMM library interface for external codes (e.g., Amber). Rework file I/O parsing to jive with multiple consecutive simulation code changes. Improve file parser error checking (numeric types). Other code clean-up.

sPuReMD: fixes for multiple consecutive simulation codepath. Reorganization to this codepath (some data structure now carry a flag to designation their allocation state). Fix bug in force field parser (atom type not truncated correctly). Charge sparse_matrix structs to be non-pointers to jive with new allocation state flag. Other code clean-up.

sPuReMD: finalize sPuReMD multiple consecutive simulation code (for integration with other codebases).

PG-PuReMD: fixes to NVT with Berendsen thermostat. Use updated constants from sPuReMD. Add BGF geometry file parser. Other code clean-up.

sPuReMD: fix memory leak with ICHOLT preconditioner (droptol for OpenMP only) for charge solver. Default to Jacobi preconditioner. Resolve several compiler warnings around C strings (snprintf, etc.). Other code clean-up.

sPuReMD: add functionality to run multiple MD simulations (for usage via integration with external codebases).

sPuReMD: resolve OpenMP build errors with GCC v10 (behavior changes for function arguments). Suppress possibly unitialized variable warnings for BiCGStab.

sPuReMD: finalize corrections for pressure calculations. Change output units from GPa to ATMs. Other formatting changes.

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).

PuReMD: backport changes for interaction function calculations. sPuReMD: alignment with PuReMD code.

sPuReMD: output PDB files according to write_freq value in control file in addition to outputting to the trajectory file. Small tweak to PDB output format to be in compliance with specification.

sPuReMD: fix issue with runs using restart files overwriting velocities to zero. Change behavor to warn if conflicting conditions exist for generating initial atom velocities. Revert formatting change of pressure logs. Enable pressure file logging when compute_pressure = 1.