Add unified script

[matthijsz]

Added unified script and utilities for it, and for the various ways of using it (logger, argument parser etc).

This is a big step toward unified analysis code for feature generation. It is a refactoring of the existing scripts to a single function, where the parameters can be passed as arguments, thus making it significantly easier to add new data sources, it is then just one more line in the config, or a few extra arguments, instead of a whole new script.

Please see the unified script section added to the readme for details on how this new function can be used. Briefly, there are three ways:

1. In batch-mode using a config (running multiple sequential datasets)
2. From command-line (for a single dataset, passing arguments via the command line)
3. From within R, using the internal function

Important to note: The old code is still present, as the config JSON to run all current public data (INPROGRESS_public_data_config.json) is currently unfinished.

Please see batch_config.json for a working example.
The output is nearly identical to that of the existing code, with the only difference being that the unified code produces more files from some of the older datasets which (in the old code) lack output that was added to the code at a later stage.