Revert "Merge remote-tracking branch 'origin/master' into GUI"

This reverts commit 9baaab70f54240ee1291f5e9b9ee45c74f09e237, reversing
changes made to e6e0421e5f30e12ed4002fc69474a39dc7081e57.

Conflicts:
	src/SendNotification.php
	src/SignUp.php
	src/classes/Event.php
	src/classes/User.php