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