Readd repair steps that are relevant when migrating from ownCloud

lib/composer/composer/autoload_classmap.php

lib/composer/composer/autoload_static.php

lib/private/Repair.php

lib/private/Repair/Owncloud/CleanPreviews.php

lib/private/Repair/Owncloud/CleanPreviewsBackgroundJob.php

lib/private/Repair/Owncloud/InstallCoreBundle.php

lib/private/Repair/Owncloud/MoveAvatars.php

lib/private/Repair/Owncloud/MoveAvatarsBackgroundJob.php

lib/private/Repair/Owncloud/UpdateLanguageCodes.php

...s/Test/Repair/Owncloud/CleanPreviewsBackgroundJobTest.php

tests/Test/Repair/Owncloud/CleanPreviewsTest.php

tests/Test/Repair/Owncloud/InstallCoreBundleTest.php

tests/Test/Repair/Owncloud/UpdateLanguageCodesTest.php