videocall: transition to videopage during a call

- transtions to the videopage during a call
- displays the called peer's name at the top of the page
- allows the user to end the call with the hangup button
- allows the user to exit and re-enter the call by selecting
  different SmartListItems

Change-Id: I48e120e9ea9bcb2498ef7a45c706e7267fd77708