Add DeviceSettings

based on https://github.com/omnirom/android_device_oppo_msm8974-common/commit/b6f6fec7884d464ebab5b11412833b8fd5dc1043

and

https://github.com/CyanogenMod/android_device_lge_g2-common/commit/d144191a5ab0233b6486edb396a778747866ca36

Change-Id: Ia5ab10b5e4a062918e1b8bfdf99cd19bfbfa63cf