Add eXtplorer v2.1 auth bypass exploit module

Add eXtplorer v2.1 authentication bypass vulnerability exploit module

* Source: http://sourceforge.net/projects/extplorer/
* Tested on:
  * 2.1.0RC5 (Standalone) (Ubuntu Linux)
  * 2.1.0 (Standalone) (Ubuntu Linux)
  * 2.1.1 (Standalone) (Ubuntu Linux)
  * 2.1.2 (Standalone) (Ubuntu Linux)

![eXtplorer v2.1 authentication bypass vulnerability exploit](http://itsecuritysolutions.org/2012-12-31-eXtplorer-v2.1-authentication-bypass-vulnerability/exploit.png)