Modifications summary:
* Moves AST-related functions from rule/utils.go to astutils/ast_utils.go (+ modifies function calls)
* Renames some of these AST-related functions
* Avoids instantiating a printer config at each call to astutils.GoFmt
* Uses astutils.IsIdent and astutils.IsPkgDotName when possible
* Refactoring on atomic rule:
-Main modification: move func gofmt to utils.go
* Refactoring on constant-logical-expr rule
Simplifies equality check of subexpressions by using gofmt function
