Small change to ruler to overrule the pretty-print order of judgements.

For example, suppose you have the following rule file:

> viewhierarchy = V
> 
> scheme expr "Expr" =
>   view V =
>     holes [ node e : Expr | | ty : Type ]
>     judgespec :- e : ty
> 
> ruleset expr.base scheme expr "Expression" =
>   rule e.app "App" =
>     view V =
>       judge A : expr = :- a : ty
>       judge F : expr = :- f : ty
>       judge B : expr = :- b : ty
>       ---
>       judge R : expr = :- (f a b) : ty

Since the judgements A, F and B are independent on each other, the order is arbitrary (probably the order of appearance in the source file).

Suppose we now want to group B and F together, such that B is pp'd directly above F. Now you can write:

> ruleset expr.base scheme expr "Expression" =
>   rule e.app "App" =
>     view V =
>       judge A : expr = :- a : ty
>       judge F : expr = :- f : ty
>       judge B : expr = :- b : ty
>       ---
>       judge R : expr = :- (f a b) : ty
>       group B F

This forces B in front of F, and A can either occur after B and F or in front.

Likewise, you can write:

> viewhierarchy = V < W
>
> ruleset expr.base scheme expr "Expression" =
>   rule e.app "App" =
>     view V =
>       judge A : expr = :- a : ty
>       judge F : expr = :- f : ty
>       judge B : expr = :- b : ty
>       ---
>       judge R : expr = :- (f a b) : ty
>       group B A F
>     view W =
>       ---
>       group F B A

to totally control the order of appearance of the judgements.