want different semantics on FileQuestion.setBaseDir() method

setBaseDir is nice, but the files which are returned are relative to that directory, making it more difficult than necessary to work with that value. Can we have a new method which is a hint to the renderer that we want to place the user in a specific initial search location, but want a value relative to the CWD? I think that's more useful in most cases I've seen.

These comments also apply to FileListQuestion of course.