Remove / re-word some settings for WiFi-only devices.

Bug: 3468248

1. Remove Wireless->Mobile networks
2. Remove Wireless->Tethering and WiFi hotspot
3. Remove Wireless->Wi-Fi Settings->Wi-Fi disconnect policy
4. Re-word Network location summary text to not include "mobile network"

Change-Id: I84a551a1b63591974731029b0d4b90a85e43a716

src/com/android/settings/Utils.java

@@ -278,4 +278,8 @@ public class Utils {
                 (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
         return telephony != null && telephony.isVoiceCapable();
     }
+
+    public static boolean isWifiOnly() {
+        return "wifi-only".equals(SystemProperties.get("ro.carrier"));
+    }
 }