[ADD] a more intuitive confidence value

[ruohoruotsi]

[ADD] a more intuitive confidence value to the results than just the PRED AVG SCORE i.e. the negative log-likelihood or the perplexity, aka exp(-PRED AVG SCORE).

It will help users understand the quality of the results better if they know and can understand the model's confidence. Perplexity is nice but perhaps not ideal for the lay technical person. Yet.

It also provides a better way to reason with developers who are using it to know when to discard and warn that the results are not worth much. 🤔