Add more biome decorators

[jimmikaelkael]

This is an extension to PR #474 (already pulled) to add more complete biome decorations so that it'll be ready when the biome grid will be functional.

Work done

• Under water block patches (sand, clay and gravel)
• Mushrooms decorator
• Trees decorator
• Improved ore populator (generates granite, diorite and andesite)
• Improved lake decorator
• Mossy stone boulder decorator
• Emerald ore decorator
• Monster eggs block populator
• Irregular bedrock layer (in order to diminish the valuable ores at the bottom)
• IceDecorator (ice patches and spikes for ice plains spikes)
• Big oak tree gen
• filled OverworldPopulator with all overworld biome variation values

Gallery link: http://imgur.com/a/YzRho

Related Links:

• Ticket: #76

[jimmikaelkael]

@turt2live I think it's ready to be reviewed.