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 of 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.

Here's the output of dbuild run:
```
[info] Project scala-------------------: SUCCESS (project rebuilt ok)
[info] Project slick-------------------: SUCCESS (project rebuilt ok)
[info] Project genjavadoc-plugin-------: SUCCESS (project rebuilt ok)
[info] Project shapeless---------------: SUCCESS (project rebuilt ok)
[info] Project json4s------------------: SUCCESS (project rebuilt ok)
[info] Project scala-partest-interface-: SUCCESS (project rebuilt ok)
[info] Project browse------------------: SUCCESS (project rebuilt ok)
[info] Project scalacheck--------------: SUCCESS (project rebuilt ok)
[info] Project scalatest---------------: SUCCESS (project rebuilt ok)
[info] Project scala-stm---------------: SUCCESS (project rebuilt ok)
[info] Project akka--------------------: SUCCESS (project rebuilt ok)
[info] Project zeromq-scala-binding----: SUCCESS (project rebuilt ok)
[info] Project scalaz------------------: SUCCESS (project rebuilt ok)
[info] Project parboiled---------------: SUCCESS (project rebuilt ok)
[info] Project sbinary-----------------: SUCCESS (project rebuilt ok)
[info] Project sbt---------------------: SUCCESS (project rebuilt ok)
[info] Project sbt-full-library--------: SUCCESS (project rebuilt ok)
[info] Project sbt-republish-----------: SUCCESS (project rebuilt ok)
[info] Project zinc--------------------: SUCCESS (project rebuilt ok)
[info] Project scala-partest-----------: SUCCESS (project rebuilt ok)
[info] Project genjavadoc--------------: SUCCESS (project rebuilt ok)
[info] Project async-------------------: SUCCESS (project rebuilt ok)
[info] Project specs2------------------: SUCCESS (project rebuilt ok)
[info] Project lift-json---------------: SUCCESS (project rebuilt ok)
[info] Project spray-json--------------: SUCCESS (project rebuilt ok)
[info] Project spray-twirl-------------: SUCCESS (project rebuilt ok)
[info] Project scala-continuations-----: SUCCESS (project rebuilt ok)
[info] Project scala-arm---------------: SUCCESS (project rebuilt ok)
[info] Project scala-io----------------: SUCCESS (project rebuilt ok)
[info] Project Play2-core--------------: SUCCESS (project rebuilt ok)
[info] Project spray-------------------: SUCCESS (project rebuilt ok)
[info] >>> The dbuild result is------------: SUCCESS (project rebuilt ok)
```