Sophisticated Backpacks: Locked by Default

On the official Cursed Walking server, we constantly get reports of first time modded minecraft players going to spawn or the market and lose everything from their backpack. They open a bug report and ask for their stuff back, but there's nothing we can do on both ends (grieflogger doesn't track removed items from backpacks being worn by players). 

Unbeknownst to these new players is the fact that Sophisticated Backpacks are open by default, rather than locked by default, which is the behavior they expect from other games.

Rather than use the server sided config which blocks open backpacks for everyone, this mod takes the more radical approach of editing the assignment of the backpack settings class's property for the default state of the "backpack open" setting. This allows backpacks to be locked by default. This resolves the problem these new players face at hopefully minimum annoyance to seasoned modded minecraft veterans who will expect backpacks to be unlocked.