ALLJOYN-1649 Winrt Chat samples hosting a channel should not have the
channel name appearing on the 'Join channel' drop down box.

This also updates the sample to handle AllJoyn API changes.

Change-Id: Ie6cfb8b70f849afde8a3ff2f53d1dc74017b60a7
ALLJOYN-1647 Update all Win8 sample programs to handle Suspending/Resuming events to release/re-acquire exclusively-held resources