[WIP] deconstructPathRelativeToSWD

Addresses fixes to deconstructPathname (addresses issue #264). Introduces a new function deconstructPathRelativeToSWD that finds the absolute path to a given path name relative to a specified working directory (swd).
Agreed. I'm open to any ideas here. Even bringing in drives is causing issues with not-Windows platforms (see the fail on the last test), and any suggestions there would be nice. Things to think about:
1. What do we even want a non-Windows machine to return if a path has a drive letter?
2. How to do tests where we might/would expect different answers on different platforms?