Map org.bukkit.Sound to String values for sending to client.

This change was done to remove the internal sound names from the API.
Along with moving the internal names into CraftBukkit, a unit test was
added for any new sounds added in the API to assure they have a non-null
mapping.

src/test/java/org/bukkit/SoundTest.java

@@ -0,0 +1,17 @@
+package org.bukkit;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.bukkit.craftbukkit.CraftSound;
+import org.junit.Test;
+
+
+public class SoundTest {
+
+    @Test
+    public void testGetSound() {
+        for (Sound sound : Sound.values()) {
+            assertNotNull(sound.name(), CraftSound.getSound(sound));
+        }
+    }
+}