Add voicemail transcriptions to Dialer

* Display voicemail transcriptions in the call log and call details
activity in the Dialer
* Fix a bug in CallDetailActivity that would result in multiple instances of    VoicemailPlaybackFragment being added on rotation. Now, reuse the same fragment
if it is already present in the FragmentManager, to avoid creating new ones
* Simplify some test and ctor logic in PhoneCallDetails to reduce the pain
of adding new fields into PhoneCallDetails
* Simplified playback_layout.xml to remove unnecessary parent LinearLayouts

Bug: 16320164

Change-Id: Ie68acc9058aace49d8e64f44a0128de0b6a3f842