Changes in CallDetailActivity to show voicemail status message.

- call details page now show a voicemail status message if the call in
  question is a voicemail and does not have audio available.
- moved VoicemailStatusHelper and related classes into
  contacts.voicemail package as it is used by CallDetailActivity as well
  as calllog.CallLogFragment

Bug: 5040099
Change-Id: I9ad0c1fb60526ef55d7f38dbd2157b14af9d5b55
7 files changed