Added the ability to pass a custom b2BodyDef

Now you can pass a custom b2BodyDef using the argument .bodyDef for more controll for the initialization of the body, ie:

var customDef = new b2BodyDef;
customDef.type = "dynamic";
customDef.position.Set(X, Y);
customDef.angle = ANGLE_IN_RADIANS;
...
craftyEntitie.box2d(bodyDef : customDef);