Simplification procedures

• introduce any a-priori simplification rules
• use the 3B and 2B consistency approach. You may start using the HullConsistency and Simp2B procedure but you may still have a lot of opportunity to produce efficient simplification procedure. For example if you have an expression like $x\sin(x)+(F(x,y)\sin(x)+G(x,y))=0$ you may write down (provided that $\sin(x)$ is a range that does not contain 0) $x=-F(x,y) -G(x,y)/\sin(x)=U$ and consider as new range for $x$ the intersection of U with the current range for $x$