Add Damageable class with basic methods

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

@@ -0,0 +1,46 @@
+/**
+ * This file is part of SpongeAPI, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2014 SpongePowered <http://spongepowered.org/>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package org.spongepowered.api.entity;
+
+public interface Damageable {
+
+    /**
+     * Damages the entity by a specified amount;
+     *
+     * @param damage the damage amount
+     */
+    void damage(double amount);
+
+    /**
+     * Gets the health of the entity
+     *
+     * @return health of the {@code Damageable}
+     */
+    double getHealth();
+
+    /**
+     * Sets the Health of the {@code Damageable}
+     */
+    void setHealth(double health);
+}

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

@@ -23,5 +23,5 @@
  */
 package org.spongepowered.api.entity;
 
-public interface LivingEntity extends Entity {
+public interface LivingEntity extends Entity, Damageable {
 }