Enable reverse tethering in BT settings screen.

- Enable support for reverse tethering in BT settings.
- Add string resource for "Auto connect" preference.
- Remove unused imports and other minor cleanups.
- Add isConnectable() and isAutoConnectable() methods to Profile
  enum type and remove isConnectableProfile() method.

Change-Id: Ie606db04028a8278e98231f0671a388671f2f067

src/com/android/settings/DockSettings.java

@@ -53,7 +53,6 @@ public class DockSettings extends SettingsPreferenceFragment {
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-        ContentResolver resolver = getContentResolver();
         addPreferencesFromResource(R.xml.dock_settings);
 
         initDockSettings();