Improvement/interface changes

Closes #282 (closed), Closes #281 (closed), Closes #283 (closed), Closes #284 (closed), Closes #248 (closed), Closes #294 (closed), Closes #247 (closed)

Show finished events in daily planning as read-only

Show event status in daily planning

Automatically add extra-availability or regular availability if a worker without availability is assigned an appointment

Ability to add appointment types

Possibility to remove appointment

Add default language to the list of languages of the subject in the flags tooltip

Issues with the interface