Reduce default settings in WifiSetup XL.

We don't want to show every configurations in default, while
we also don't want to complicate basic wifi logics. In order to
achive both goals, we first introduce tweaked xml file
(wifi_config_preference2.xml). It does contain all the
config components but almost all of them are in "gone" visibility.
Those components are still able to act as data storage, but never
be seen as actual UI components.

Change-Id: I4ad3c1b4cbbe77ca2b628b0be25e2b3eb9d645aa