Major updates to change default behavior of NDN to connect to a random host on the testbed.
Make expressInterest and registerPrefix connect when needed.  Removed WebSocketTransport.connectWebSocket.
Also, don't fetch the ccndid until registerPrefix needs it.
Use the default NDN() to connect to a random host on the testbed.
Remove the call to connectWebSocket.
Don't disable the button, since we connect after clicking it.
When creating the NDN, don't need to set host to null since this is now the default.