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* Add WifiSettingsForSetupWizardXL as a new Activity
The activity has WifiSettings fragment in it. It also contains
several buttons, texts around the fragment.

* Making configuration UI part of Preference list.
In Wifi Setup for Setup Wizard XL, WifiSettings fragment lets
a UI for configuring access points shown inside a
PregerenceCategory object, while it has been shown as Dialog.

To achieve this action, WifiDialog is decomposed into two parts:
- WifiConfigUiBase (Mainly UI part)
- WifiConfigController (Mainly Wifi controller part)

All codes for wifi configuration in WifiDialog is now in
WifiConfigController, which is reused from
WifiConfigPreference.

* Misc stuff
- Remove AccessPoint#compareTo(). Instead,
  AccessPoint.AccessPointComparater should be used when needed.

Change-Id: I520d690d3301837d32f91dad54a973a379ce1989