remove old unused renderer files
jsonrpc: cleanup JSON-RPC API definition
videodb: add RemoveArtForItem()
jsonrpc: add possibility to remove artwork from video items
Merge pull request #3347 from MartijnKaijser/old_renderers

remove old unused XBOX renderer files
Merge pull request #3519 from Montellese/jsonrpc_art_removal

jsonrpc: add possibility to remove artwork from video items