Update header.php

Added another webpage tab called Approve users, that links to approve_user.php
TEST!
Merge remote-tracking branch 'origin/master'

Conflicts:
	header.php
niks bijzonders
Merge remote-tracking branch 'refs/remotes/origin/master'
Added a stylesheet for the approve user page
Merge remote-tracking branch 'origin/master'

Conflicts:
	agenda.php
	css/calendar.css
	css/style.css
	footer.php
	header.php
Edited the approve_user.php page, fixed the session bug, and cleaned up the logout.php page.