code: function (e) {
              if (this.dragging === true) {
                  this.pos.set(e.gameX, e.gameY, this.pos.z); //TODO : z ?
                  this.pos.sub(this.grabOffset);
              }
          }
docs: Gets called when the user drags this entity around
  @name dragMove
  @memberOf me.DraggableEntity
  @function
  @param {Object} x the pointer event