Allow running Scala scripts (as well as Scala classes)

* If tries running it as a script and if it fails, it falls back on
running as a Vert.x verticle class implementation.
* The Scala interpreter verbose levels can be controlled with
vertx.scala.interpreter.verbose system property
* Provided a unit test that verifies that both scripts and Scala
classes can be compiled and run accordingly.
code review + put all scripts (VerticleClass!) into src/test/scripts
fix build script stuff to be able to use TestVerticle