Snowy Tundra improvements

Just like the plains the snowy tundra is rather devoid of character and atmosphere.

One small change of course would be to have parity between the 2 versions with snow, taking the bedrock snow logging and applying it to Java.

Another would be to add rocks, boulders, and sage as nice decorative blocks throughout the tundra.

Sages could grow out from the snow caps and be a cute little plant, which if sheered, can give thorns for all sorts of crafting and potion possibilities. For instance the thorns could be used to craft a thorn block, which could damage entities that walk on the block, even while crouched.