Added support for the new iTunes distributed object notification. It is

Added support for the new iTunes distributed object notification. It is
caught at iTunesRemote, which then sends a notification.
MainController will switch over from polling to the new method as soon as
it receives the first notification. One side effect of this is that the
"No Song Playing." status window no longer shows when iTunes stops, but
that's just too bad.
I also added an option to keep polling, as default "UsePollingOnly"
When using the distributed notifications, I disable disabling the status
item when iTunes stops responding, and instead throw a menu saying iTunes is
not responding.