Add CVE-2014-6271 exploit via Pure-FTPd ext-auth
Remove the less stable echo stager from the exploit
Release fixes, all titles and descs
Update pureftpd bash module rank and description
Add CVE-2014-6278 support

Going with an OptEnum to simplify the code for now...
Land #3927 - Shellshock PureFPTd extauth
Adds support for both CVEs, lands #3931
Land #3928, release fixes