2.0 dev streams

I tried to clean up a bit and converted everything to streams, made better use of models and libraries (imho).
So it should get easiery to write new features tec.

It's not nearly finished yet, but I wanted to give a heads up - in form of pull request :) - so no one else starts working on that stuff.

The module basically works - I've only tested the backend, creating topics and replies in the frontend - but there's still a lot to clean up.