removed unused functions and broken method World.prototype.clone, related to https://github.com/schteppe/p2.js/issues/165
removed unused functions and broken method World.prototype.clone, related to https://github.com/schteppe/p2.js/issues/165

koopero/p2.js,mcanthony/p2.js,psalaets/p2.js,koopero/p2.js,psalaets/p2.js,modulexcite/p2.js,mcanthony/p2.js,markware/p2.js,beni55/p2.js,modulexcite/p2.js,markware/p2.js,beni55/p2.js