Create Settings app object
Migrate airplane mode, bluetooth and cell data settings tests to the app
Migrate language and keyboard language tests to the app
Migrate do not track, gps, and media storage
Migrate passcode, wallpaper and wifi

Use self.apps.displayed_app instead of passing app to panel

Update to address review comments:
- change Airplane mode switch locator
- remove unnecessary parentheses
Merge pull request #1033 from bobsilverberg/settings_app2

Create Settings app object