Merge changes for launching wifidisplay from system settings

1. wifidisplay: Use ExtendedRemoteDisplay to launch Wifi Display.
- RemoteDisplay class is used to launch WiFi Display
  implementation in the Android framework with a discovered peer.
  There is a need to support proprietary implementation of wifi
  display instead of the framework implementation.
- To enable this support, ExtendedRemoteDisplay is added,
  which launches the proprietary solution. ExtendedRemoteDisplay object
  is created if the class is available in the package. If the class is
  not available the default implementation will be used by creating
  RemoteDisplay.

Change-Id: I2e2a5e552bc86888848c0402bafd873620b05c21

2. wifidisplay: Modify WifiDisplayController
Spawn RTSP server before P2P connection
--In order to be sanguine that the RTSP server has been spawned
  on source, invoke listen() before P2P connection.
--Add a debug property to enable verbose logging in WifiDisplayController
Block teardown to avoid severing P2P group
--Since WFD dispose is asysnchronous, framework proceeds with teardown
  and dissolves P2P group before WFD stack is able to complete message
  exchange for teardown.
--Prevent framework from doing so and allow it to proceed only once
  WFD stack indicates it's dependence on network is over.
Add null check guards in WifiDisplayController
--The WifiP2PGroup delivered in the onGroupInfoAvailable() callback
  is not guaranteed to be non-null and hence needs to be validated.
--The same applies to the WFDDevice that is retrieved using
  info.getOwner()

CRs-Fixed: 1041702
Change-Id: Ie0e23ba42c1afe42662943cd864ab3077a156e0a