Add Play2-core, spray, scala-async and many more

This collective work of me and @retronym. We've been busy tweaking dbuild to cover larger number of open source projects. We managed to cover the whole sbt, Play 2 core, entire spray and number of dependencies on those projects (this list includes only projects being added by this PR):

  * scala-continuations
  * parboiled
  * json4s
  * lift-json
  * spray-twirl
  * spray-json
  * scala-io
  * scala-arm
  * shapeless 2.0
  * specs2

With this PR, dbuild covers over 900k lines of Scala code. This comprehensive coverage allowed us to discover and fix several regressions. Although the configuration is a bit messy I feel we should merge it as-is and clean up gradually later on.