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"
You should never use `return` like this in Scala.

This is better:

```scala

galleryElements find { galleryElement =>
  isPictureGallery(galleryElement)
} map {
  new FaciaGalleryItem(galleryElement)
} getOrElse {
  throw new RuntimeException("Could not find any picture gallery elements")
}
```