Convert to using platform independent filenames/paths

[zaneselvans]

Right now there are some hard coded paths referring to data files within the project. Mostly they currently assume a Unix/OSX type filesystem. They should be made platform agnostic, using the os.path module.

[zaneselvans]

This has mostly been taken care of with the ferc1.py and pudl.py modules using os.path. There are now global variables in settings.py that indicate the location of data directories within the project for various purposes, and lower level directories are constructed with os.path.join. Might still need to weed out some remaining messes. Also use of automated scripts for downloading data and cleaning up the paths made this cleaner and simpler (getting rid of UPLOADERS and the other intervening directoires in the FERC Form 1 for instance).