Introduce scoobi-thrift module

I probably have this wrong in so many ways. It might just be easier to create a separate `scoobi-core` project. 

The part I'm mostly worried about is the `rootSettings` which I copied from `specs2`. I don't know if it's a good idea - it seems to compile everything twice. Alternatively I'm wondering how hard it would be to fix the ivy dependencies of the root project to depend on all the aggregrate projects, which seems like a much cleaner way of doing this (looks like this happens for Ambiata projects - promulgate perhaps?).

/cc @etorreborre