[1/2] LED customization

* Add LED customization.
* Add global and per-app settings.
* Set default LED color as white.
* Remove stock on/off checkbox and add an dedicated category.
* Remove dead code from display settings.

[1/2] 个性化LED

* 添加LED个性化.
* 添加全局和各个应用的设置.
* 设置默认LED颜色为白色.
* 删除原生开/关勾选框, 并添加一个独立分类.
* 删除显示设置中的无用代码.

[2/2] in platform_packages_apps_Settings

Thanks to CyanogenMod for the original implementation.
感谢CyanogenMod原创实现此功能.