Multiple function estimates with a single call, file naming changes, IWLS fixes

Fixed various issues where the IWLS estimator would produce -nan values, resulting in crashes in other functions
Estimating more than one stream can now be performed on multiple functions by using the -c switch.
Changed stream output filenames to reference the original filename so that experimentation can be done more easily. Should also be easier to find which files go together.
Functions for checking presence of and creating directories.
Experimenter takes input and output directories as parameters and outputs separate experiments to separate directories in the output directory.