Add two new intents

Add an ACTION_DEFAULT_SMS_PACKAGE_CHANGED intent to notify the old and
the new default sms app of the change. Add an ACTION_EXTERNAL_PROVIDER_CHANGE
intent used to notify the default SMS app when another whitelisted app
(such as AndroidAuto [via bluetooth] or the phone) changes the SmsProvider
or MmsProvider behind the default SMS's back.

Change-Id: Id036b1313124f08ff1d48b306e68b5f457d235c7