Heightfield bugs/issues

[schteppe]

1. The body angle does not affect Heightfield vs Circle collisions at all
2. The WebGL demo renderer does not handle rendering heightfields with local shape offsets
3. there's no support for Heightfield in world.hitTest()
4. When colliding Heightfield vs Circle, there's some contact points missing. See demo code below

        var app = new p2.WebGLRenderer(function(){

            var world = new p2.World({
                gravity : [0,-10]
            });

            this.setWorld(world);

            var shape = new p2.Heightfield({heights:[0,100,80,200,130,50,70,150,100,100,160], elementWidth: 50 });
            var body = new p2.Body();
            body.addShape(shape);
            world.addBody(body);

            var circle = new p2.Circle({ radius: 40 });
            var body = new p2.Body({ mass: 1, position: [100, 300] });
            body.addShape(circle);
            world.addBody(body);
        });