CBGP Redux. Removes schema-inference.

[erp12]

Improvements:

• Hooks
• Clarified terminology:
  • Expr
  • ATS: A Expr and it's type
  • Unit
  • Gene
  • Param vs Arg
• Pull simplified type system into the repo.
• Maps -> Records
• Baked-in chunk of push for Abs and Let to avoid skipping push code.
• Simplified problem definitions and benchmark CLI