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"
sorry -

```scala
map { galleryElement =>
  new FaciaGalleryItem(galleryElement)
}
```

This can also be done more concisely:

```scala
galleryElements.find(isPictureGallery).map(new FaciaGalleryItem(_)) getOrElse {
  throw new RuntimeException("Could not find any picture gallery elements")
} 
```