Adds option to toggle preservation of item stack density.

[TinkerWorX]

Adds a toggle option for item stack density, to allow the player to transport more items on fewer trains and store more items in storage.

The option defaults to off to preserve the default balance of the mod.

I added locale keys to the other locales in English, I can remove those if it's better to not have the keys for now.

Feel free to close this PR if it isn't a desired feature, it was a quick change that I'm using locally at the moment as an alternative to the much heavier OmniCompression.

[Deadlock989]

This isn't something I'd want to see in the mod if I'm honest, but as long as the toggle is off by default I don't mind if shane wants to add it.

[shanemadden]

Sorry I didn't see this PR months ago, whoops - thanks for the bump to remind me, @Deadlock989

The feature you're looking for is actually already implemented as a (default-disabled) option in my separate 'experiments' mod, for people who want this kind of balance adjustment - without having to add yet more potentially confusing config options to the base mod.

I think that should cover what you're looking for without needing to run local tweaks, let me know if not!