Add module for the vbulletin exploit in the wild

Module for http://www.net-security.org/secworld.php?id=15743

~~Please don't land still, test in progress.~~

Verification steps:

- [x] Install Ubuntu 10.04 (or other system)
- [ ] Install vBulletin 4.1.0 or 4.1.5. Test with other vulnerable versions (branches ~~4.x~~ 4.1.x and 5.x) is super welcome. 
- [x] Run the module
- [ ] Check if the user has been really created successfully. Admin access should be granted to the vBulletin platform.

Test on real instances of vBulletin would be super welcome, I'm trying to find someone to help with it.