Removed Opening and Closing historical artifacts.

Issue #540

The build fails due Scala compiler error I don't understand:

```
[ant:scalac] RxJava\language-adaptors\rxjava-scala\src\main\s
cala\rx\lang\scala\Observable.scala:531: error: type mismatch;
[ant:scalac]  found   : x2.type (with underlying type rx.Observable[_ <: T])
[ant:scalac]  required: T
[ant:scalac]       Observable[T](x2)
[ant:scalac]                     ^
[ant:scalac] one error found
```

```scala
  def window[Closing](closings: () => Observable[Closing]): Observable[Observable[T]] = {
    val func : Func0[_ <: rx.Observable[_ <: Closing]] = closings().asJavaObservable
    val o1: rx.Observable[_ <: rx.Observable[_]] = asJavaObservable.window[Closing](func)
    val o2 = Observable[rx.Observable[_]](o1).map((x: rx.Observable[_]) => {
      val x2 = x.asInstanceOf[rx.Observable[_ <: T]]
      Observable[T](x2)
    })
    o2
  }
```

Could someone help me with this?