Rename and move skip season entry after watched entries.

- Drop 'episode' and 'season' from 'Skip <x>'.
- Reorder season context menu entries.
Add skipped suffix to watchedbox icons.

- New ic_action_watch_skipped drawables.
- Modified WatchedBox to have a new state: skipped.
- Update EpisodesAdapter and UpcomingFragments adapter.
- Use CheatSheet on WatchedBox.