Add ability to show/hide different device information.

This introduces 3 boolean flags:

config_show_device_model
config_show_wifi_ip_address
config_show_wifi_mac_address

Which when set to false will hide their individual panes from "About
Phone" page.

Bug: 62414913
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=com.android.settings.deviceinfo
Change-Id: Iaaf91ef41c9ec7b5bf233344e6a48d4b87fad291

tests/robotests/src/com/android/settings/deviceinfo/DeviceModelPreferenceControllerTest.java

@@ -69,10 +69,16 @@ public class DeviceModelPreferenceControllerTest {
     }
 
     @Test
-    public void isAlwaysAvailable() {
+    public void isAvailable_returnTrueIfVisible() {
         assertThat(mController.isAvailable()).isTrue();
     }
 
+    @Test
+    @Config(qualifiers = "mcc999")
+    public void isAvailable_returnFalseIfNotVisible() {
+        assertThat(mController.isAvailable()).isFalse();
+    }
+
     @Test
     public void displayPref_shouldSetSummary() {
         mController.displayPreference(mPreferenceScreen);