Adjust naming of left vacation days in overview

* If remaining vacation days have been expired, show how many of the
  days have been expired instead of having a message that shows only
  that they are expired.

* refs #18007
Add error page for access denied error (403 status code)

* refs #18083
Remove menu from error page

* refs #18083
Set title of the app hard instead of by properties

* To avoid stacktrace when error pages are fetched, set the title of the
  app not by properties.

* refs #18083
Fix wrong calculation of used days sum

* When calculating used days, it's not enough to use the application's
  days to sum the days because applications at the turn of the year have
  to be considered.

* refs #18008
Change redirect link to staff list after create/edit a person

* refs #18086
Remove obsolete controller constants and methods

* refs #18086
Show existent working times in person form when more than one

* refs #18086
Adjust naming of left vacation days on app detail page

* refs #18007
Show latest applications and sick notes at first in overview

* refs #18016
Add placeholder to working time valid from input field

* refs #18086
Set date and number formats hard to german

* Since the application is available only in german language,
  the format of dates and numbers should be in german too.

* It would be nice to internationalize the application one day, then the
  format of dates and numbers should depend on the browser locale.

* refs #18017
Fix wrong styling for cancelled applications in list
Make used days in overview null-safe

* If a person has no applications yet, the number of used days should be
  0.

* refs #18007
Set locale app wide to german locale

* refs #18017
Release version 2.0.4
Prepare for next development iteration