[WifiSetup] Use setup navigation bar

Use the setup navigation bar in wifi setup activity.

1. Include frameworks/opt/setupwizard/navigationbar/common.mk in the
make file.
2. Make WifiSetupActivity implement NavigationBarListener
3. Added the fragment in setup_preference.xml, wrapping the whole
screen in a LinearLayout
4. Moved skip and next screen logic to WifiSetupActivity, refactored
the skip dialogs into a fragment

Change-Id: Ia973c0a61faa3ead201bd10d5aa8de4bc6e091c1