Bug fix in printing of clauses list. Commented out problematic code used to respect layout of operators.
Moved imports of help files to the rule assertions
Fixed display of required extra parenthesis (comp_priority+fix_position_if_braced)
Added test 24 with a right behavior about parenthesis
Fixed tests, related to bad parenthesis fixing, fixed valid_op_type_arity, which have sense only for arity 1 (TODO: arity 2).