Split the importer module out from the installer module (#468)

* Split the importer module out from the installer module

* Cleanup of unused imports

* Move updater into separate module #453

* Remove unused imports/formatting

* Disable the install and importer modules at the end of the setup

* Unused imports; update IJ style

* test explicit stage for php+mysql

* add more to matrix

* Add different MariaDB versions

* undo

modules/Importer/Config/config.php

@@ -0,0 +1,7 @@
+<?php
+
+return [
+    'importer' => [
+        'batch_size' => 20,
+    ],
+];