attributes are not sorted in the output formula

[yegor256]

When a formula is printed after rewrite command, attributes in bindings are not sorted (if I'm not mistaken). This causes confusion while testing. I suggest sorting them alphabetically.

[yegor256]

@deemp please, check

[deemp]

@fizruk, please check.

I see two ways to implement this:

1. Use ordered maps instead of lists in the AST

   eo-phi-normalizer/eo-phi-normalizer/grammar/EO/Phi/Syntax.cf

   Lines 51 to 52 in 9338f09

   	Formation. Object ::= "⟦" [Binding] "⟧" ;
   	Application. Object ::= Object "(" [Binding] ")" ;

2. Recursively traverse an expression and sort attributes before printing

What can be other ways? Which one is more preferrable?

[fizruk]

@yegor256 ordering is important for void attributes (since $\alpha_i$ in applications explicitly refer to that order). We can sort attached attributes, however.

@deemp It might be best to use Map for attached attributes (and then do toAscList), but void attributes need to retain order as specified in the source code (so use lists).

[yegor256]

@fizruk no matter what algorithm you use in sorting, it will work. We just need persistency between between versions of normalizer.

[yegor256]

@fizruk let's close this, in favor of this: #629