[Metadata] Make release year of tracks available

[hideman2]

Problem:
I would like to play the pop songs of the 80's.

There query using the spotify client would look like this:

year:1980-1989 genre:pop

I won't find Eddy Grants' Electric Avenue, released in 1982, because the original album "Killer on the Rampage" is not available on Spotify. Instead this track appears on the Album "100 Essential Hits, Vol. 2", released in 2010 and some other ones but none of them was released in the 80's.

Originally, I have created this issue for the Spotify Web Api https://github.com/spotify/web-api/issues/363 but actually this seems to be a general problem of your meta data model. This is not a feature request, this is a bug.

If all albums of all artist were available this bug would not occur. But since you are missing some data, you can't rely on the release date anymore.

(For the advanced music listener) the orignal release year of a song is one of the most important attributes for selecting the music (right after the genre). If the same song is on more than one album or has been remastered, it still has to hold the orignal release year and preferably the original released album.