Change the loop behavior to something that is actually sensible,
with [ ] looping the whole playlist and [ 1 ] looping the song.
This also removes the "Do on end" setting. A new stop option may
be reintroduced, however.
This resolves issue #13.
Collapse amber and yellow into a single accent [Yellow], remove the neutral accent due to UI isuses, and darken light-mode accents across the board to be more visible.
