ui: add starred toggle buttons to shows list items

this allows shows to be starred/unstarred directly from the shows list
without having to go to the show's details.
ui: remove starred/unstarred section headers

...from the shows list. it's now obvious why starred shows are sorted above
unstarred shows (because each show has a star toggle next to it), so the
headers aren't necessary any more.
ignore specials when marking show as watched

...or unwatched. from the menu items in the show activity.

most of the time I haven't seen most of the specials even if I've seen
all the episodes, so it's more useful to me this way.
ui: display episode number in episode list

display the episode's number before its title when viewing a season's
episodes.
bump version to 0.5