Refactor oven to make operations more modular. Move some pig specific ones to pigpen-pig.
Fix quoting bug in script generation
Only DataBag supports accumulation & returning bags. Move accumulator & add explicit bag creation.
Call seq on the results of all co-groupings to enforce consistency
Fix order-dependent tests
Fix rank adjustments locally to match pig
Move rx functional tests to rx. Add pig functional tests.
Merge branch 'functional-tests' into local-mode

* functional-tests:
  Move rx functional tests to rx. Add pig functional tests.
  Fix rank adjustments locally to match pig
  Fix order-dependent tests
  Call seq on the results of all co-groupings to enforce consistency
  Only DataBag supports accumulation & returning bags. Move accumulator & add explicit bag creation.
  Fix quoting bug in script generation
  Refactor oven to make operations more modular. Move some pig specific ones to pigpen-pig.