dragStart(e) {
		if (this.dragging === false) {
			this.dragging = true;
			this.grabOffset.set(e.gameX, e.gameY);
			this.grabOffset.sub(this.pos);
			return false;
		}
	}
Gets called when the user starts dragging the entity
@param {object} e - the pointer event
@returns {boolean} false if the object is being dragged