Added new plugin for local fanart based on MediaItem paths

Removed ThumbnailAspects from Default skin, all loaded via FanArtImageSource now
Extended fanart types, removed online MDEs from Client project
Added ImageSourceFactory to allow plugins to add support for new sources.
Made LocalFanartProvider more relaxed, accepting any media type
Removed FanartImageSources for normal MediaItems (now supported mapping in server side providers)