Scala test fw

First attempt to use the inhouse Scala testing framework with one test for checking the picture overlay functionality. Keep in mind that I am a beginner Scala dev so code will likely look very "Javaish"
```scala
galleryImages find { image =>
  image.isDisplayed
}
```

Or even more concisely, and more readably ... 

```scala
galleryImages.find(_.isDisplayed)
```