Settings: porting N code

1. Change all default language strings contains "WLAN" to "Wi-Fi".
2. Add overlay config to show Alert Dialog and cancel button
3. shows dialog when open wifi while WIFI_Tethering open
4. Display summary "Share your device's mobile data connection via USB
or a Mobile HotSpot" under Tethering & Mobile HotSpot

Change-Id: Ie8533970472222ed837272d976723c049e0e948b
CRs-Fixed: 1039259