Reduce processing steps, standardize source filenames

* SOURCE_FILE is now standardized to be the original filename from Forte
(no more extension mapping)
* Consolidated awk_files() loop into unzip_files() and renamed to
process_files()
* Along with this, eliminated the set of intermediary files -- leaving
simply "unprocessed" (/dl) and "processed" (/pr) files.
Merge pull request #2 from dsquier/add-features

Reduce processing steps, standardize source filenames