CI: Minimal modifications to allow it to work

I am a big fan of NCrunch and I would like to use it to work on the issues about CSS naming so I made the smallest adjustments needed to allow it to work well.

Based on [this post (last answer](http://social.msdn.microsoft.com/Forums/en-US/540c2273-2ad3-4a48-93ba-5fa6bda8c941/team-build-does-not-understand-devenvdir), and [this blog post](http://blogs.clariusconsulting.net/kzu/devenvdir-considered-harmful/) it's better, in a CI point of view, to use $(VS120COMNTOOLS) instead of $(DevEnvDir)

It's still possible to launch an Experimental Instance of VS to debug and the output directory is still the same so, as far as can say, there is no impact other that allowing NCrunch to work now.