Moved demon slayer cutscene trigger to its own MapArea

Server/src/main/kotlin/api/ContentAPI.kt

@@ -751,6 +751,10 @@ fun <T> setAttribute(entity: Entity, attribute: String, value: T) {
     entity.setAttribute(attribute, value)
 }
 
+fun removeAttribute(entity: Entity, attribute: String) {
+    entity.removeAttribute(attribute)
+}
+
 /**
  * Locks the given entity for the given number of ticks
  * @param entity the entity to lock

Server/src/main/kotlin/api/MapArea.kt

@@ -11,7 +11,7 @@ import core.game.world.map.zone.ZoneRestriction
  * Interface that allows a class to define a map area.
  * Optionally-overridable methods include [getRestrictions], [areaEnter], [areaLeave] and [entityStep]
  */
-interface MapArea {
+interface MapArea : ContentInterface {
     var zone: MapZone
         get(){
             return zoneMaps[this.javaClass.simpleName + "MapArea"]!!
@@ -29,4 +29,4 @@ interface MapArea {
     companion object {
         val zoneMaps = HashMap<String, MapZone>()
     }
-}
+}