- Ensight places restrictions both on variable names and on file
  names. When generating the variable to file name correspondence for
  use in the Ensight case file, previously used the less stringent
  variable name for both sides of the variable table.

  This would lead to situations where the (valid) variable name
  referred to the wrong file name. Now apply the file-name restriction
  consistently when creating the variable table. This is especially
  necessary since the stem of the filename additionally has
  specific characters (eg, ":<>[]") that can be problematic for the
  shell or file-system.

ENH: avoid repeated '_' in qualified ensight names.

- when replacing undesirable characters (eg, ":<>[]") with '_', avoid
  duplicates.

  Eg, "PaSR<psiReactionThermo>:Qdot" becomes
      "PaSR_psiReactionThermo_Qdot" instead of
      "PaSR_psiReactionThermo__Qdot"

ENH: additional ensightCase::padded static method