Revert "fix: get rid of undeclared timezones in caldav ics files"

This reverts commit 6f0ec0acf3ae9143e7a1f15b288edcf87ed318fb.

Conflicts:
	lib/object.php
make it possible to set saturday as first day of the week
use own loading.gif, loading.gif is to big in core now
fix deleting event and fix php notices
Don't change timezone of datetime-objects with datetype local