Add getState(NPCState)

Adds NPC#getState(NPCState) to return a boolean indicating whether the NPC in question has a specific state.

api/src/main/java/net/jitse/npclib/api/NPC.java

@@ -101,6 +101,14 @@ public interface NPC {
      * @return Object instance.
      */
     NPC toggleState(NPCState state);
+    
+    /**
+     * Get state of NPC.
+     *
+     * @param state The state requested.
+     * @return boolean on/off status.
+     */
+    boolean getState(NPCState state);
 
     /**
      * Change the item in the inventory of the NPC.