Adding a "None" setting to "Drop Items on Disconnect" setting

[Survivalist83]

Currently, under World Settings, our two options for the "Drop Items on Disconnect" setting are "Default" and "Everything." This works great for multiplayer: a player can't just log out and steal Chester or the Celestial Orb for the rest of the server.

I mostly play singleplayer, and I would like to see an additional option, "None," where we can keep the unique items like the Eye Bone or the Celestial Orb in our inventories when we log out. In singleplayer, there is nobody I'm stealing Chester from when I'm logged out. Not having "None" just gives me the extra step of remembering to pick up the Eye Bone every time I log in, and if I forget, it's a big headache.