ENH: several improvements to foamEtcFile

- lazier evaluation of project name and version based on the directory
  name. Avoids heuristics based on directory names unless really needed.

- cope with alternative directory locations.
  For example, OpenFOAM+VERSION etc.

The combination of the two above appears to be sufficient to open up
the directory naming possibilities.

- additional -list-test option (tests for existence of directory).