'ad_hoc_works#approval_status' to display datetime_end

app/assets/stylesheets/style.css
- Add '#table_ad_hoc_works_approval_status .datetime_end'.
app/controllers/ad_hoc_works_controller.rb
- Add 'datetime_end' to COLUMN_NAMES_TO_DISPLAY_IN_APPROVAL_STATUS.
config/locales/ja.yml
- Add "datetime_end" under "activerecord.attributes.ad_hoc_work".
Fix ApplicationHelper::first_line() not to return empty string

app/helpers/application_helper.rb
- Fix first_line() to skip a newline at the start of the
  string in order to prevent returning an empty string.
'ad_hoc_works#approval_status' to display caption of table

app/assets/stylesheets/style.css
- Add '#table_ad_hoc_works_approval_status caption'.
app/views/ad_hoc_works/approval_status.html.erb
- Add <caption> to the table.
'ad_hoc_works#approval_status' to handle status of 'Drafting'

app/assets/stylesheets/style.css
- Add '#table_ad_hoc_works_approval_status .Drafting'.
config/locales/ja.yml
- Add "Drafting" under "activerecord.values.ad_hoc_works.approval".
(tmp) Rename files with "ad_hoc_works..." to "approval_statuses..."

app/assets/javascripts/ad_hoc_works.js.coffee
app/assets/stylesheets/ad_hoc_works.css.scss
app/controllers/ad_hoc_works_controller.rb
app/helpers/ad_hoc_works_helper.rb
app/views/ad_hoc_works/approval_status.html.erb
- Renamed old files.
app/assets/javascripts/approval_statuses.js.coffee
app/assets/stylesheets/approval_statuses.css.scss
app/controllers/approval_statuses_controller.rb
app/helpers/approval_statuses_helper.rb
app/views/ad_hoc_works/index.html.erb
- New files after renaming.
Finish moving 'ad_hoc_works#approval_status' to 'approval_statuses#index'

app/controllers/approval_statuses_controller.rb
- Rename the class to ApprovalStatusesController.
- Rename approval_status() to index(), and rename @column_names
  to @column_names_for_ad_hoc_works.
app/helpers/approval_statuses_helper.rb
- Rename the class to ApprovalStatusesHelper.
app/views/ad_hoc_works/index.html.erb
app/views/approval_statuses/index.html.erb
- Renamed to the latter.
config/routes.rb
- Add resources route :approval_statuses.
Finish 'approval_statuses#index' for contents

app/assets/stylesheets/style.css
- Add '#table_work_plans_approval_status .approval_status',
  '#table_work_plans_approval_status .drafting',
  '#table_work_plans_approval_status .finished',
  '#table_work_plans_approval_status .maint_approved' and
  '#table_work_plans_approval_status .prod_approved'.
- Adjust the colors for 'approval_statuses#index'.
app/controllers/approval_statuses_controller.rb
- Add COLUMN_NAMES_TO_DISPLAY_FOR_WORK_PLAN.
- Modify index() to prepare @work_plans.
app/helpers/approval_statuses_helper.rb
- Modify displaying_value() and displaying_css_class() for
  more general use.
app/models/work_plan.rb
- Add scope :before_enddate and :latest_first.
app/views/approval_statuses/index.html.erb
- Extract the <table> to partial '_status_table'.
config/locales/ja.yml
- Add "approval_statuses.index" under "helpers.page_title".
- Add "table_caption.*" under "helpers".
app/views/approval_statuses/_status_table.html.erb
- Newly created, taking over the contents from view
  'approval_statuses#index'.
Layout template to display links to other pages

app/assets/stylesheets/style.css
- Add 'a.button_link, a.button_link:visited'.
app/helpers/application_helper.rb
- Add main_links().
app/views/general_logbooks/index.html.erb
- Replace link to 'work_plans#' with links in layout template.
app/views/layouts/application.html.erb
- Add ApplicationHelper::main_links() call.
app/views/work_plans/index.html.erb
- Replace link to 'general_logbooks#' with links in layout template.
config/locales/ja.yml
- Add "approval_statuses.index" under "helpers.link".