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/module.json

@@ -0,0 +1,14 @@
+{
+    "name": "Importer",
+    "alias": "importer",
+    "description": "",
+    "keywords": [],
+    "active": 1,
+    "order": 0,
+    "providers": [
+        "Modules\\Importer\\Providers\\ImporterServiceProvider"
+    ],
+    "aliases": {},
+    "files": [],
+    "requires": []
+}