Merge branch 'split' into 8.x-1.x

migrate_example/README.txt

migrate_source_csv/migrate_source_csv.info.yml

migrate_source_csv/src/CSVFileObject.php

migrate_source_csv/src/Plugin/migrate/source/CSV.php

migrate_source_csv/tests/src/Unit/CSVUnitTestCase.php

...urce_csv/tests/src/Unit/Plugin/migrate/source/CSVTest.php

migrate_tools/migrate_tools.drush.inc

migrate_tools/migrate_tools.info.yml

migrate_tools/migrate_tools.links.action.yml

migrate_tools/migrate_tools.links.menu.yml

migrate_tools/migrate_tools.module

migrate_tools/migrate_tools.permissions.yml

migrate_tools/migrate_tools.routing.yml

migrate_tools/src/Controller/MessageController.php

migrate_tools/src/Controller/MigrationGroupListBuilder.php

migrate_tools/src/Controller/MigrationListBuilder.php

migrate_tools/src/DrushLogMigrateMessage.php

migrate_tools/src/Form/MigrationAddForm.php

migrate_tools/src/Form/MigrationDeleteForm.php

migrate_tools/src/Form/MigrationEditForm.php