'projects#index' to hide/show progresses on user request

app/controllers/projects_controller.rb
- Modify index() to prepare @shows_progresses.
- Add switch_shows_progresses().
app/views/projects/index.html.erb
- Modify to hide progress unless @shows_progresses.
- Add link to switch @shows_progresses.
config/locales/ja.yml
- Add "show_no_progress" and "show_progresses" under
  "helpers.label.project".
config/routes.rb
- Add collection route 'switch_shows_progresses' to resources :projects.
db/migrate/20110107073543_create_user_specifics.rb
- Add COLUMN shows_progresses to TABLE user_specifics.