Simple plugin, that allow players to break only leaves and vines. no commands, no configs. You can download it here. versoin 0.2: You can download it here. Added config and commands. Todo: /hgame start. It must tp all players on start positions. Tp points will be set in config.yml, like breakable block now.
About documentation: What I can document, when plugin has no config? Customization added. Sources will be soon.
Autostart is bad idea because after fifth player can join sixth player. I think that the best way is integration with MultiWorld, but I'm not so good in java.