Added fake entropy graph plot at offset 0 to ensure a full graph even if the entire file has high entropy

Updated unpfs extractor to create unique output directories in the event of multiple PFS images inside the same file; added directory traversal check.

Changed the reported name of raw signatures to 'Raw signature' so that --dd option can be used to extract arbitrary raw signatures

setup.py now creates version.py which defines the current binwalk version (with git commit hash, if avaliable)