Revert "Merge branch 'feature/install-wizard-6136'"

This reverts commit 88d4262e7ca17430eb2385715f402becfc653797, reversing
changes made to 6fae333048d0ef2b95f52c8113143c79e10c4e50.

Conflicts:

	application/controllers/InstallController.php
	library/Icinga/Web/Controller/ActionController.php