WIP, integration almost complete. ALS benchmark very close to running.

What's missing:
- need a few more custom picklers (eg BlockManagerId & friends)
- need to add a Kryo-style registrator, for convenient registration of
  user-defined types.
- should move OutputStreamOutput into pickling
- need to determine if the type information of ClassTags is enough to create
  suitable internal FastTypeTag when unpickling