'projects#index' to display unfinished Progress's instead of last

app/helpers/application_helper.rb
- Modify ball_holder_display() to use Progress#finished?().
app/models/progress.rb
- Add finished?().
app/views/projects/index.html.erb
- Change to display all unfinished Progress's if
  @shows_last_progress_only is true.
config/locales/ja.yml
- Change the value for
  "helpers.link.projects.show_last_progress_only".