Adds new minimal Spoofax project

Did some minor tweaks on the generated .gitignore:
  * adds syntax/Scala*.generated.pp
  * changes scala.jar to scala-java.jar
Adds first draft of Scala grammar in SDF

Rules are mainly taken from appendix A of The Scala Language
Specification Version 2.9 (DRAFT May 24, 2011).

The rules need further tweaking to make them Spoofax-compatible – the
project does not build in the current form.