Add Dock USB Audio Support for Samsung Car / Desk Docks 1 of 2

Samsung docks have a non-sensing USB adio port.
Samsung get around this by having a separate Setting to route the Audio
The Changes made will only add the extra Observer if the Kernel supports the endpoint

  /sys/class/switch/dock/state

A new BroadcastReciever (SettingsChangedReceiver) is used to watch out for users changing the Preference

The choice is made in the GalaxyS2Settings.apk (see 2 of 2)

  device/samsung/i9100/DeviceSettings/src/com/cyanogenmod/settings/device/DockFragmentActivity.java

After OnBootComplete and when the checkbox is changed, an Intent is triggered to this class.

When a Dock Event is caught if it is one the Samsung endpoint "dock" then if the users preference is checked,
then the event is allowed to go on and route the audio.  If it is not checked then it is ignored.

Change-Id: Id43af5a13d04e96645ccc49292518107aa4af98e