extend the data with some usable properties like scale, rotate, velocity etc
@param {Object} manager
@param {Object} input
function computeInputData(manager, input) {
        var session = manager.session;
        var pointers = input.pointers;
        var pointersLength = pointers.length;

        // store the first input to calculate the distance and direction
        if (!session.firstInput) {
            session.firstInput = simpleCloneInputData(input);
        }

        // to compute scale and rotation we need to store the multiple touches
        if (pointersLength > 1 && !session.firstMultiple) {
            session.firstMultiple = simpleCloneInputData(input);
        } else if (pointersLength === 1) {
            session.firstMultiple = false;
        }

        var firstInput = session.firstInput;
        var firstMultiple = session.firstMultiple;
        var offsetCenter = firstMultiple ? firstMultiple.center : firstInput.center;

        var center = input.center = getCenter(pointers);
        input.timeStamp = now();
        input.deltaTime = input.timeStamp - firstInput.timeStamp;

        input.angle = getAngle(offsetCenter, center);
        input.distance = getDistance(offsetCenter, center);

        computeDeltaXY(session, input);
        input.offsetDirection = getDirection(input.deltaX, input.deltaY);

        var overallVelocity = getVelocity(input.deltaTime, input.deltaX, input.deltaY);
        input.overallVelocityX = overallVelocity.x;
        input.overallVelocityY = overallVelocity.y;
        input.overallVelocity = abs(overallVelocity.x) > abs(overallVelocity.y) ? overallVelocity.x : overallVelocity.y;

        input.scale = firstMultiple ? getScale(firstMultiple.pointers, pointers) : 1;
        input.rotation = firstMultiple ? getRotation(firstMultiple.pointers, pointers) : 0;

        input.maxPointers = !session.prevInput ? input.pointers.length : input.pointers.length > session.prevInput.maxPointers ? input.pointers.length : session.prevInput.maxPointers;

        computeIntervalInputData(session, input);

        // find the correct target
        var target = manager.element;
        if (hasParent(input.srcEvent.target, target)) {
            target = input.srcEvent.target;
        }
        input.target = target;
    }