Add 'operator' Intention: Support header/impl functions

#KT-18851 Fixed

idea/testData/multiModuleQuickFix/addOperatorByHeader/js/js.kt

@@ -0,0 +1,5 @@
+impl class Foo {
+    impl fun unaryMinus() {
+
+    }
+}

idea/testData/multiModuleQuickFix/addOperatorByHeader/js/js.kt.after

@@ -0,0 +1,5 @@
+impl class Foo {
+    impl operator fun unaryMinus() {
+
+    }
+}