Add EAP/802.1X configuration for WiFi Setting.

1. Remove the isEnterprise() filter in Scanresult.
2. This requires the new fields such as identity, eap, certificate/key
to support EAP authentication in Wifi Settings.
3. Add simple file-based keystore to select the cert/key from UI.

-- Updated from the comments.
-- Fix the bug for passing null pointer for adding spinner items.