Generate 'toString()': Permit for data classes

#KT-14122 Fixed

idea/testData/codeInsight/generate/toString/common/dataClass.kt

@@ -1,2 +0,0 @@
-// NOT_APPLICABLE
-data class A<caret>(val n: Int)

idea/testData/codeInsight/generate/toString/multipeTemplates/dataClass.kt

@@ -0,0 +1,2 @@
+// GENERATOR: MULTIPLE_TEMPLATES
+data class A<caret>(val n: Int, val s: String?)

idea/testData/codeInsight/generate/toString/multipeTemplates/dataClass.kt.after

@@ -0,0 +1,9 @@
+// GENERATOR: MULTIPLE_TEMPLATES
+data class A(val n: Int, val s: String?) {
+    override fun toString(): String {
+        return "A(" +
+                "n=$n," +
+                "s=$s" +
+                ")"
+    }
+}

idea/testData/codeInsight/generate/toString/singleTemplate/dataClass.kt

@@ -0,0 +1,2 @@
+// GENERATOR: SINGLE_TEMPLATE
+data class A<caret>(val n: Int, val s: String?)

idea/testData/codeInsight/generate/toString/singleTemplate/dataClass.kt.after

@@ -0,0 +1,6 @@
+// GENERATOR: SINGLE_TEMPLATE
+data class A(val n: Int, val s: String?) {
+    override fun toString(): String {
+        return "A(n=$n, s=$s)"
+    }
+}