Fix many issues with the Tutorial Island plugin

Amongst other things, this:
* Stops the player from trying to leave the Runescape Guide's house if
  they have yet to speak to him.
* Fixes the hint icon for both the Runescape Guide and the door.
* Ensures all files pass rubocop.
* Generally improves the code throughout the plugin.

data/plugins/location/tutorial-island/plugin.xml

@@ -17,7 +17,8 @@
   </scripts>
   <dependencies>
     <dependency>dialogue</dependency>
+    <dependency>door</dependency>
     <dependency>entity-spawning</dependency>
     <dependency>quest</dependency>
   </dependencies>
-</plugin>
+</plugin>