Bedrock cave and mountain generation in Java, too.

A lot of the exclusive cave and mountain generation is in bedrock edition, and it would be cool to have them in Java as well. Some mountains should have the flat peaks, not all of them, though. These would be called flatpeaks. These would be used as building platforms, if you want to set up a base in the mountains. There should also be much rarer mountains that can extend up to the build limit, and be much steeper than the ones found lower down.