More Masteria quests + several minor fixes

Added more quests on Masteria and updated drop data in the region. Fixed
mystic door on slopes deploying players unproperly. Fixed mounts
equipped by low level players crashing the client.

src/server/maps/MapleMap.java

@@ -433,6 +433,11 @@ public class MapleMap {
         }
         return ret;
     }
+    
+    public boolean canDeployDoor(Point pos) {
+        Point toStep = calcPointBelow(pos);
+        return toStep != null && toStep.distance(pos) < 20;
+    }
 
     private void dropFromMonster(final MapleCharacter chr, final MapleMonster mob) {
         if (mob.dropsDisabled() || !dropsOn) {