Windows: Several visual changes to SongGridView to make it cleaner. No more grid lines except for each album. No more artist/album captions over album art. No more mouse over color change. A bit sad that I took a lot of amount of time to do these features a few years ago... to realize they are more noise than useful. But after these changes... I think my designer was right! Added a bit of logic to PlaylistPresenter.

Related to issue #422.