Add input and output file directories to the config.yaml file

[trevorb1]

It would be good to add inputDir and outputDir variables to the config file (similar to whats in the snakefile) that all the scripts call. That way if we ever change directory naming its not a tedious task where we have to change paths in all the scrips

ie. Instead of having

in the config.yaml file we would have:
outputDir = '../src/data/

then the script would read in the value from the config file and the line would be (checking syntax of creating the file path like that)
df.to_csv(outputDir + 'SpecifiedDemandProfile.csv', index=False)

[tniet]

Use os.path.join to make it OS independent and more future proof:
df.to_csv(os.path.join(outputDir, 'SpecifiedDemandProvide.csv'), index=False)