Enforce Cause to never be empty, removed now unnecessary EmptyCause and

PresentCause as Cause itself can remain it's own implementation.

Signed-off-by: Gabriel Harris-Rouquette <gabizou@me.com>

src/main/java/org/spongepowered/api/data/translator/ConfigurateTranslator.java

@@ -84,7 +84,6 @@ private static void translateMapOrList(ConfigurationNode node, DataView containe
         } else if (value != null) {
             container.set(of(node.getKey().toString()), value);
         }
-
     }
 
     @Override

src/main/java/org/spongepowered/api/entity/Entity.java

@@ -303,7 +303,7 @@ public interface Entity extends Identifiable, DataHolder, DataSerializable {
      * @return True if damaging the entity was successful
      */
     default boolean damage(double damage, DamageSource damageSource) {
-        return damage(damage, damageSource, Cause.of());
+        return damage(damage, damageSource, Cause.of(NamedCause.source(damageSource)));
     }
 
     /**

src/main/java/org/spongepowered/api/event/SpongeEventFactory.java

@@ -4459,14 +4459,12 @@ public static LoadWorldEvent createLoadWorldEvent(Cause cause, World targetWorld
      * Creates a new instance of
      * {@link org.spongepowered.api.event.world.SaveWorldEvent}.
      * 
-     * @param game The game
      * @param cause The cause
      * @param targetWorld The target world
      * @return A new save world event
      */
-    public static SaveWorldEvent createSaveWorldEvent(Game game, Cause cause, World targetWorld) {
+    public static SaveWorldEvent createSaveWorldEvent(Cause cause, World targetWorld) {
         Map<String, Object> values = Maps.newHashMap();
-        values.put("game", game);
         values.put("cause", cause);
         values.put("targetWorld", targetWorld);
         return SpongeEventFactoryUtils.createEventImpl(SaveWorldEvent.class, values);