Figure out call-by-need shifts for Levy

[clayrat]

https://pdfs.semanticscholar.org/bfce/015374fb798fa98e37e646db524ba47b5835.pdf Ariola, Herbelin, Saurin, "Classical Call-by-need and duality" http://ix.cs.uoregon.edu/~pdownen/publications/classical-need-artifacts.pdf Ariola, Downen, Herbelin, Nakata, Saurin, "Classical call-by-need sequent calculi: The unity of semantic artifacts" http://ix.cs.uoregon.edu/~pdownen/publications/csl18_short.pdf Downen, Ariola, "Beyond Polarity: Towards A Multi-Discipline Intermediate Language with Sharing"