Add short date format with weekday

This is used in the coursebook (absences & probably statistics). It also seems more usefull then the version with the long weekday.

changed milestone to /AlekSIS%"[NLnet #3 (closed)] Implement support for absences"

assigned to @permcu

created branch 1034-add-short-date-format-with-weekday to address this issue

mentioned in merge request !1491 (merged)

closed with merge request !1491 (merged)

mentioned in commit 79ea1a63