Support RepeatMode

[LukePulverenti]

In the latest nuget:

When you report playback start & progress, there is now a RepeatMode property. It defaults to RepeatNone but also accepts RepeatOne and RepeatAll.

In order to receive a remote control command to change report mode, add SetRepeatMode to your supported commands list. it will then come through as a GeneralCommand with a RepeatMode argument.

In order to remote control other apps, RepeatMode has been added to SessionInfo.PlayState