Feature for enabling/disabling wizard steps based on certain conditions

I have done the basic coding for enabling / disabling wizard steps based on dynamic conditions. I have created the unit tests as well to validate that nothing breaks and also to demonstrate usage of this feature.

Please note that I had to add jQuery as a dependency to the karma configuration as jQLite was not enough for some of the DOM operations

Also, I added PhantomJS launcher and Jasmine to the node dependencies as the current configuration perhaps assumes them as globals. You can choose whether or not to accept this bit.