Add notes about read only classes (exercism#3095)

- Adds Javadocs to Character and Destination classes in Wizards and Warriors 2
  and the Item class in Knapsack to let students working offline know that
  they are treated as read only by the test runners.
- TavelMethod made editable to allow students to experiment with making changes
  to the enum.

Changes in commit does not change outcome of tests.

[no important files changed]

Resolves exercism#3092

Author: kahgoh

exercises/concept/wizards-and-warriors-2/.meta/config.json

@@ -8,7 +8,8 @@
   ],
   "files": {
     "solution": [
-      "src/main/java/GameMaster.java"
+      "src/main/java/GameMaster.java",
+      "src/main/java/TravelMethod.java"
     ],
     "test": [
       "src/test/java/GameMasterTest.java"
@@ -18,8 +19,7 @@
     ],
     "editor": [
       "src/main/java/Character.java",
-      "src/main/java/Destination.java",
-      "src/main/java/TravelMethod.java"
+      "src/main/java/Destination.java"
     ],
     "invalidator": [
       "build.gradle"

exercises/concept/wizards-and-warriors-2/src/main/java/Character.java

@@ -1,3 +1,8 @@
+/**
+ * Represents a Character in the game.
+ *
+ * NOTE: There is no need to change this file and is treated as read only by the Exercism test runners.
+ */
 public class Character {
     private String characterClass;
     private int level;

exercises/concept/wizards-and-warriors-2/src/main/java/Destination.java

@@ -1,3 +1,8 @@
+/**
+ * Represents a Destination.
+ *
+ * NOTE: There is no need to change this file and is treated as read only by the Exercism test runners.
+ */
 public class Destination {
     private String name;
     private int inhabitants;

exercises/practice/knapsack/.meta/src/reference/java/Item.java

@@ -1,3 +1,8 @@
+/**
+ * Represents an item that can be placed in the knapsack.
+ *
+ * NOTE: There is no need to change this file and is treated as read only by the Exercism test runners.
+ */
 class Item {
 
     // Weight of the item