Update PMS Status once Idle

[meskibob]

I finished watching a video with PMS about two hours ago, and afterwards I shutdown the PS3. PMS still says that the "PS3 has been found" under the Status tab. Something like an idle timer, where once PMS has stopped streaming/transcoding any data for say 5 minutes, it occasionally pings the last used PS3 IP to see if it's still there. If the ping fails, update the status icon.

[meskibob]

Bump