Selecting elements in the library list start that song playing. Yay!
Current version is slightly broken, and in a somewhat silly way. No idea
whether two players will actually be necessary (or even useful), but I
would like to shoot for seamless playback if at all possible. Anyway,
things aren't quite set up properly for using this double buffer of sorts,
so there's a bit of broken components, but nothing too tricky to fix. Next
up: check for when a song ends, so I can progress to the next song in the
list.
Fixed up a bit of layout so the seekBar doesn't look like garbage. Also
set up hooks so that the seekBar will update properly, and will allow you
to track through the song - yay! Also, I've got gapless playback working!
There's some messiness in getting that to work exactly as intended, but it
does, indeed, do what it's supposed to if everything works. Huzzah!

Next up: getting the library model to properly return me the next song,
then adding back/forward buttons.
Began the process of sorting songs. That is, I'm currently sorting by
titles, and I've put in a (fairly) modular setup for sorting them in
different fashions later. Next up: properly selecting a song from the
list, and adding back/forward buttons (finally)