Add estimation of context-sensitive probability of sufficiency to the explainable reasoning module

[rfl-urbaniak]

• consequent_differs is now consequent_neq and a symmetric function, consequent_eq has been introduced.
• added consequent_eq_neq that scatters appropriately gathered values of the other consequent... functions.
• a new type of intervention is defined, sufficiency_intervention which deterministically (unlike preemption) intervenes with the factual values.
• a new handler, SearchForNS has been introduced with a test thereof.