Fix featureList not update issue.

The problem rooted in model synchronization.

You're using `PBManager` as shared manager & model (which I doubt is a good idea) and in your `PBArrayDataSource`, you recreated an `NSArray *item`, so you'll have to house-keeping both data, and that'll be a problem.

I've removed the `item` property with a shared instance of `PBManager`, and it just work.

BTW, I highly recommend split `PBManager` because now it has TWO responsibilities, which is bad. How about a `PBDataCenter`?