Adding ForbiddenGreaterClause to the package

[Deathn0t]

Hello,

I wanted to know if there is a good reason for not having a ForbiddenGreaterThanClause / ForbiddenLessThanClause.

I started drafting the former and it works fine. Are you interested in a PR?

I am attaching the (draft) code here (could be integrated within the package):

custom_forbidden.py.zip