Remove more entries not relevant to wifi-only devices.

Bug: 3488384
Bug: 3487976
Bug: 3488381

Removed Cell standby entry from Battery use screen.
Removed Mobile signal strength from BatteryHistory screen.
Added wifi IP address to About->Status
Remove auto-timezone checkbox in Settings->Date & time

Change-Id: I228721a3613b1aeb600026e42274337886552698