Allow NPCs to be damaged and killed

Server/src/main/java/net/simon987/server/game/Attackable.java

@@ -0,0 +1,19 @@
+package net.simon987.server.game;
+
+/**
+ * Objects that can be attacked or healed
+ */
+public interface Attackable {
+
+    void setHealRate(int hp);
+
+    int getHp();
+    void setHp(int hp);
+
+    int getMaxHp();
+    void setMaxHp(int hp);
+
+    void heal(int amount);
+    void damage(int amount);
+
+}