PATCH SET 2:
+ Add import com.android.settings.R
PATCH SET 3:
+ Remove @Override interface methods to be compilable by Java 1.5.
PATCH SET 4:
+ Add import android.net.vpn.VpnManager
PATCH SET 5:
+ Add license headers.
PATCH SET 6:
+ Remove Constant.java and move the constants to VpnSettings.
+ Make AuthenticationActor implement DialogInterface's handlers.
+ Remove trailing spaces.
PATCH SET 7:
+ Remove default username.
