Generate equals/hashCode(): Enable for classes without properties

Also:
- forbid for enum classes
- use javaClass.hashCode() instead of 0 if class has no properties

 #KT-18418 Fixed

idea/testData/codeInsight/generate/equalsWithHashCode/noVarsWithSuperClass.kt

@@ -0,0 +1,10 @@
+open class X {
+    override fun equals(other: Any?) = super.equals(other)
+    override fun hashCode() = super.hashCode()
+}
+
+class A : X() {<caret>
+    fun foo() {
+
+    }
+}