Implement Binomial potential

[Iñigo Bermejo]

This type of potential will be applicable to node X when X is binary and it only has a numeric parent. The potential will not have any parameters. The projection of this potential to a table will only be possible when the parent node has a numeric value assigned.

[Francisco Javier Díez]

I do not know why Iñigo proposed creating this potential. We have been able to do without it for 6 years, so I'm closing this issue.