[1/2] Alternative screen-off animations

Add alternative screen-off animations.
Now users are allowed to choose from the following options:
* Fade out
* Electron beam[CRT screen-off] (default)
* Scale down

[1/2] 备用关屏动画

添加备用关屏动画.
现在用户可在下列选项中选取:
* 淡出
* 电子光束[CRT显示器关屏] (默认)
* 收缩

[2/2] in platform_packages_apps_Settings

Add alternative screen-off animations.
Now users are allowed to choose from the following options:
* Fade out
* Electron beam (default)
* Scale down