- split images into two basic layers:
    1. OS + packages
    2. OpenFOAM repo/packages

  This allows better reuse of layer 1 between different OpenFOAM
  versions.

- create images with version tagging.

  Previously had images such as openfoam2112-run, openfoam2106-run etc.
  However this will get out of control in the very near future.

  Now just use the standard image tagging for the OpenFOAM versions,
  which also benefits from the common base layer 1 for the images.

  Old  -> New
  openfoam2112-run -> openfoam-run:2112 (and openfoam-run:latest)
  openfoam2106-run -> openfoam-run:2106

ENH: add --shm-size as pass-through option

- needed for intelmpi (eg, --shm-size=4G)