These backdoors/shells are mostly from Michael Daw's excellent "Web Backdoor Compilation" which can be
found at http://michaeldaw.org/projects/web-backdoor-compilation.

To enable a new backdoor file for upload, simple drop it here and make sure the extension matches
whichever type of language it is. For example, a JSP backdoor should be named... something.jsp.

If multiple files are present for a language, they will all be uploaded when appropriate.