Remove whitespace generation (#5833)

* Remove whitespace generation and rely on default printing

Changes to printing:
* Add newline after last empty SwitchCase
* Add newlines around block comments if they are non-flow comments or contain newlines

* Fix a few more fixtures

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-superClass/expected.js

@@ -11,6 +11,7 @@ let A = function (_B) {
     } else {
       var _this = _B.call(this) || this;
     }
+
     return _this;
   }