Allows thumbnail generation for TV recordings in multiseat if the TV recording folder is shared.

Now using .net remoting

https://github.com/MediaPortal/MediaPortal-1/tree/EXP-4060-THUMBNAIL_Remoting

Needs to add configuration on server side for tiling options for thumbs, and needs to be linked to the 3920 fix to use a single ffmpeg binary for both MP and TV.