Add working express.Static middleware

Hello! I've noticed `js.npm.connect.Static` doesn't work, because it produces JS `require("connect")["static"]` which is undefined. I don't know if it's a difference in versions, so I didn't remove the `js.npm.connect.Static` class, but I did add a `js.npm.express.Static` class with correct namespace. (Producing `require("express")["static"] instead.)

Before, with this code:
```haxe
import js.npm.connect.Static;
// (...)
app.use(new Static(Node.__dirname + "/public"));
```

Node complains:
```
var middleware = new (Static__6||require("connect").static)(js.Node.__dirnam
		                 ^
TypeError: undefined is not a function
```

After changing the initial import to `js.npm.express.Static` it works.