Conjectures for non-implications using invariants

Stream: Equational

[Anand Rao Tadipatri]

I've opened PR equational#389 that adds a list of conjectures for non-implications based on the metatheorem suggested by @Hernan Ibarra.

I think the PR in its current form is ready for review, and I would like to soon follow it up with a PR generating more conjectures based on other invariants, and another PR providing automatic proofs for these conjectures.