54775754 model to idf output erroneously deleted

@elainethale this fixes the ModelToIdf output file deletion problems you were seeing on both windows and linux.

Problems are two fold: possible case differences between 'c:' and 'C:' on windows and possible "double completion" of output path names when relative output paths are used.

I opened this pull request into your branch instead of develop to make it easier for testing, on your side.

-Jason