Edited Feature: add ActionButton helper [275]

Sometimes I want an ActionLink to show up as a button. An edit button that goes to /Item/Edit/1 comes to mind. My solution is to create a helper that takes exactly the same parameters as ActionLink, but renders as a button: ActionButton.

I have the code. This issue is here to "track the work and make a decision on whether the helper fits with the goals and plans for MVC" as Eilon Lipton writes in http://aspnetwebstack.codeplex.com/discussions/361785