- ensures that unloading will not affect the rest of the table

- ADIOS-2.4.0 and earlier had timeName.bp files
  and timeName.bp.dir/ directories. Restart checked for
  times based on the timeName.bp files

- ADIOS-2.5.0 and later simply use timeName/ directories,
  for which we can use slight modifications of standard
  OpenFOAM fileOperation routines.

Does not handle mixed naming. If the .bp files exist, we assume that
they provide full coverage for restart.

- a silent change, but taken in advance of C++20

- defaults to user locations

- handle -prefix=DIR for specifying installation locations outside of
  the regular OpenFOAM tree.

- from the naming and layout of the ADIOS file variables, there
  is not much in common with the previous integration for adios1.
  Therefore managing in a new repository.