feature request : handling instruments and instrumentists

[simoncn]

MinimServer treats all tags the same for indexing purposes, with some special processing of the combination of AlbumArtist and Artist when creating the Artist index. Album is special because it is used to group tracks within an album. Other tags including Composer and Genre have no special treatment. In no case does MinimServer attempt to parse the contents of a tag value and give special semantics to these contents.