Less automatical evaluation for Equality, improve simplification

fixes #6116

see also #7960
I like this!  But we should find a test for it.  (one that does not simplify without this).  
````
Lt(y + cos(x)**2, z + 1 - sin(x)**2)
````
I think I expect `y - z < 0` but `y < z` should be even better.  Neither seems to work right now :(