Edited Issue: Add support to attribute routing for ignoring the route prefix [1150]

AttributeRouting.net has an option for ignoring the route prefix:

```
[RoutePrefix("Prefix")]
public class IgnorePrefixController : Controller
{
[GET("Index")] // => "Prefix/Index"
[GET("NoPrefix", IgnoreRotuePrefix = true)] // => "NoPrefix"
public ActionResult Index() { /* ... */ }
}
```

It's really convenient to be able to add a route for an action without having to worry about existing route prefixes. This is like having absolute and relative URI paths.

Maybe we could use a leading slash as a way to indicate an absolute route path?:
```
[RoutePrefix("Prefix")]
public class IgnorePrefixController : Controller
{
[GET("Index")] // => "Prefix/Index"
[GET("/NoPrefix")] // => "NoPrefix"
public ActionResult Index() { /* ... */ }
}
```