Saves NPCs immediately after they are changed

Additionally:
Updates Citizens dependency to the newest version
Removes some redundancy in NPC settings' path

src/main/java/net/knarcraft/blacksmith/BlacksmithPlugin.java

@@ -88,10 +88,10 @@ public class BlacksmithPlugin extends JavaPlugin {
         registerListeners();
 
         getLogger().log(Level.INFO, " v" + getDescription().getVersion() + " enabled.");
-        //TODO: Default blacksmith trait aren't saved to the config file. One way to fix this would be to display the
-        // default value as the current value if the current value is null, as it's effectively the actual value.
-        // Additionally, this would allow NPC settings to update when the default is changed, as long as no custom
-        // value has been set.
+        //TODO: Improve un-setting of values for a given NPC: While setting values works fine, a bit more care should
+        // be performed regarding removing a custom value. Basically, using null for strings and -1 for numbers should
+        // unset a value for an NPC. Unsetting a value would make the NPC use the default value set in the config file
+        // instead
     }
 
     /**