Introduce SwitchBar widget

- SwitchBar is a LinearLayout that containts a TextView and a Switch and
is intended to replace all Switches that are put in the ActionBar as a
custom view
- use the new SwitchBar for WifiSetting only for now (a later CL will
take care of all the other Setting that are using a Switch in the
ActionBar)

Related to bug #14898161 On/Off switches must move down from Action Bar

Change-Id: I5e98dbe995bba8f440d08459e09ca3ac09d3464b