xbmc/xbmc — pull request #1840 by Montellese (2012-11-24 14:17:08+00:00)
Title: JSON-RPC: attempt to fix the artist mess

These commits are an attempt to fix the current mess with the link between albums/songs and artists in JSON-RPC (as discussed in the internal forum). The following changes are made:
* add "genreid" property as an array of IDs to AudioLibrary.GetAlbums/GetAlbumDetails/GetSongs/GetSongDetails
* add "artistid" property as an array of IDs to AudioLibrary.GetAlbums/GetAlbumDetails/GetSongs/GetSongDetails
* change "artist" property from an array of strings to a concatenated string of artists
* remove "albumartist" property from AudioLibrary.GetSongs/GetSongDetails

For me the following two questions need to be discussed and answered before this can be merged:
* Does the "genreid" property make sense? First of all it is only really there to make it easier to do an offline synchronisation in a client. Second it's not supported everywhere i.e. not in AudioLibrary.GetArtists/GetArtistDetails and also not in the VideoLibrary methods.
* Should "artist" be an array of strings or a concatenated string? Should we keep "artist" as an array of strings and instead add a new property "displayartist" or something like that which provides a string like "Linkin Park feat. Jay Z" (once that's supported)?