Add helper method to find absorbing frames about pikov HOT 1 CLOSED

-- Select the final frame in each clip.
-- See max-value-in-group: https://stackoverflow.com/a/7745635/101923
SELECT f1.clip_id, f1.clip_order
FROM frame AS f1
LEFT OUTER JOIN frame AS f2
  ON f1.clip_id = f2.clip_id
  AND f1.clip_order < f2.clip_order
-- Join with transitions to find frames with no transitions out.
LEFT OUTER JOIN transition
  ON f1.clip_id = transition.source_clip_id
  AND f1.clip_order = transition.source_clip_order
  AND (
    f1.clip_id != transition.target_clip_id
    OR f1.clip_order != transition.target_clip_order
  )
WHERE f2.clip_order IS NULL  -- No next frame.
  AND transition.source_clip_order IS NULL;  --  No transitions out.