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"
A bit better, but still don't use a `var` for capabilities.

If you don't want to make an intermediate case class to wrap the capabilities and driver, you can just just use a `Tuple`:

```scala
val (driver, capabilities) = getProperty(Browser) match {
  case "firefox" =>
    val capabilities = initDesiredCapabilities(testCaseName, DesiredCapabilities.firefox())
    (new FirefoxDriver(capabilities), capabilities)
  // ... ETC
}
```