ENH: add options for foamEtcFile and shell evaluation

- Eg, instead

      if file=$(foamEtcFile filename)
      then
          . $file
      fi

  can write

      eval "$(foamEtcFile -sh filename)"

  Also supports -verbose reporting, which is especially useful for csh,
  since it allows simplification of aliases and allows the message to
  land on stderr instead of stdout.

      eval `foamEtcFile -csh -verbose filename`