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/explicitDefaultAccessors.kt

@@ -5,6 +5,4 @@ class Test {
     var name: String = ""
         get
     <caret>
-}
-
-// FORCED
+}

idea/testData/codeInsight/generate/equalsWithHashCode/explicitDefaultAccessors.kt.after

@@ -12,9 +12,7 @@ class Test {
     }
 
     override fun hashCode(): Int {
-        return 0
+        return javaClass.hashCode()
     }
 
-}
-
-// FORCED
+}

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

@@ -1,4 +1,3 @@
-// NOT_APPLICABLE
 class A {<caret>
     fun foo() {
 

idea/testData/codeInsight/generate/equalsWithHashCode/noVars.kt.after

@@ -1,4 +1,3 @@
-// FORCED
 class A {
     fun foo() {
 
@@ -11,6 +10,6 @@ class A {
     }
 
     override fun hashCode(): Int {
-        return 0
+        return javaClass.hashCode()
     }
 }

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

@@ -1,6 +0,0 @@
-// FORCED
-class A {<caret>
-    fun foo() {
-
-    }
-}

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

@@ -1,4 +1,3 @@
-// FORCED
 open class X {
     override fun equals(other: Any?) = super.equals(other)
     override fun hashCode() = super.hashCode()

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

@@ -1,4 +1,3 @@
-// FORCED
 open class X {
     override fun equals(other: Any?) = super.equals(other)
     override fun hashCode() = super.hashCode()