Experimental DB pool + fixed stat overflow on equips

Implemented EXPERIMENTAL DBCP (connection pool), trying to improve
concorrent access to DB. Added door portals on Kerning Square. Fixed
equipments getting stat overflow when upgrading stats. Fixed expiring
pets crashing the client in some cases.

src/server/MapleStorage.java

@@ -61,11 +61,14 @@ public class MapleStorage {
 
     private static MapleStorage create(int id, int world) {
         try {
-            try (PreparedStatement ps = DatabaseConnection.getConnection().prepareStatement("INSERT INTO storages (accountid, world, slots, meso) VALUES (?, ?, 4, 0)")) {
+            Connection con = DatabaseConnection.getConnection();
+            try (PreparedStatement ps = con.prepareStatement("INSERT INTO storages (accountid, world, slots, meso) VALUES (?, ?, 4, 0)")) {
                 ps.setInt(1, id);
                 ps.setInt(2, world);
                 ps.executeUpdate();
             }
+            
+            con.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
@@ -84,6 +87,7 @@ public class MapleStorage {
             if (!rs.next()) {
                 rs.close();
                 ps.close();
+                con.close();
                 return create(id, world);
             } else {
                 storeId = rs.getInt("storageid");
@@ -94,6 +98,8 @@ public class MapleStorage {
                     ret.items.add(item.getLeft());
                 }
             }
+            
+            con.close();
         } catch (SQLException ex) {
             ex.printStackTrace();
         }