disable tweeners when desktop-effects are disabled

* set tweener animation time to 0.001 seconds when desktop effects are disabled.  0 seemed to break callbacks.
* add support for FORCE_ANIMATION boolean parameter to enable the
animation even when desktop effects are disabled.  I chose the capital letters so any use of it will be questioned.

Example usage of FORCE_ANIMATION:
```javascript
Tweener.addTween(this, {
            opacity: 255,
            xOffset: 0,
            yOffset: 0,
            transition: 'linear',
            onComplete: onComplete,
            FORCE_ANIMATION: true,
            time: POPUP_ANIMATION_TIME });
```