[2/2] Lockscreen targets customization

Add user configurable lockscreen targets / icons.

[2/2] 个性化锁屏目标

添加用户可配置的锁屏目标/图标.

[1/2] in platform_frameworks_base

Thanks to CyanogenMod(@Danesh) for the original implementation.
感谢CyanogenMod(@Danesh)原创实现此功能.