Make admin credentials available on built images

[obilodeau]

Admin credentials should be stored in the Vagrantfile that is packaged in the box. I don't see a security issue doing so and I see a usability issue not doing so.

Let me elaborate. I've built Win 7 images a long time ago, with a config I have changed since. Now trying to use these boxes I can't without manually changing the password because I lost the admin password. Having that password in the box file would have helped me.