Replace DenseRowTextStorage with raw mr job

@markhibberd I haven't done anything significant here (yet), expect for order the dictionary the way it was. I'm assuming there is more we want to do as well but you didn't get time. I'm happy to finish it up, and might look more closely at what you've done after lunch.

/cc @raronson 
> It doesn't need to be deterministic across runs.

Well it makes it a little hard to test, both in the spec and in the cli tests. :(