HOLIDAYREQ-15: Create new 'Comment' and 'Type of holidays' fields

HOLIDAYREQ-16: Overview doesn't work when the employee account is deleted

HOLIDAYREQ-17: Improve the display of pages and mails

HOLIDAYREQ-18: Change 'Days' field type to float

HOLIDAYREQ-19: Add a 'Calendar' page
[Misc] Align POM with best practices
HOLIDAYREQ-19: Add a 'Calendar' page

Fix an issue with the Calendar