API Review PhoneManager -> TelecommManager. Rename methods (5/6)

PhoneManager
- handlePinMMI docs should explain what a Pin is and what MMI is
- rename isInAPhoneCall to isInCall
- rename showCallScreen to showInCallScreen
- merge this class into TelecommManager, we don't need both

Bug: 16960458

Change-Id: I7a31cbe97ba6ca48c038dd9bfb18da3ad724239d