Relational: if simplify lhs/rhs not enough, try harder with .equals(0)

Call _eval_sides.  This used to happen in Relational __new__ so now
we have the essentially the same code.  If an expression previously
reduced to bool upon constructor, it should now do so after simplify().
Ineq: fix tests that fail due to ineq not simplifying [2/n] (squash)

Just add `simplify` around those inequalities.
Ineq: fix tests that fail due to ineq not simplifying [3/n] (squash)

remove comments