PG-PuReMD: remove outdated debugging and validation code (was performing host-only simulation with host+device simulation and comparing results).

sPuReMD: fix issue with configure script nuking Tensorflow link variables when LAPACK link variables are set.

sPuReMD: refactoring to better align with PuReMD code. PuReMD: backport sPuReMD changes from validation efforts against Fortran ReaxFF code.

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