Fix @return array PHPDocs, in /lib

lib/private/app.php

lib/private/appconfig.php

lib/private/config.php

lib/private/contactsmanager.php

lib/private/files/cache/cache.php

lib/private/files/cache/scanner.php

lib/private/files/cache/updater.php

lib/private/files/filesystem.php

lib/private/files/view.php

lib/private/group.php

lib/private/group/backend.php

lib/private/group/database.php

lib/private/group/dummy.php

lib/private/group/example.php

lib/private/group/interface.php

lib/private/group/manager.php

lib/private/legacy/appconfig.php

lib/private/legacy/config.php

lib/private/legacy/preferences.php

lib/private/migrate.php