API Review PhoneManager -> TelecommManager. Rename methods (1/6)

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: I6d1939175c0292641f6ece0b630db8a864871d7e