Display connection and playback status in surface

[adamantivm]

Show some indication of what is the current state of the received transmission:

• No packets are being received
• Packets are being received but not decoded
• Stream is being received properly
• Timeout receiving packets?

The main idea is to give some indication of what is going on when something goes wrong, or when the stream stops being received (i.e.: because connection was lost).

Ideas:

• Show a message saying: "No connect" overlaid on the surface when there is no connection?
• When playing a video and suddenly there is no more connection, display a "disconnected" sign?

Also, this issue could be divided in two parts:

1. Add error and/or status notifications via listeners to the RtpMediaPlayer, for users of it
2. Actual display of those status updates to the user in Mission Control or in the example player