Add artistId to Child element in API

[ShinikVeech]

Sindre-

I am presently working on a .Net implementation of a Windows client (it is around alpha at this point), and I noticed that the Child type does not have a reference to its parent's parent. This means that when a song is returned as a search result, there is no way to traverse upward to its artist node.

Alternatively to this, adding a parent attribute (that holds the parent's id) to the directory node that returns from getMusicDirectory.view would alleviate the issue as well. However, this would require a second call to determine the artist id from a search result, so this would be less desirable than the first option.

Please let me know if you have any questions about this.

Thanks!

Mark