Barcode refactor (#363)

* Move barcode.dart

* Fix

* Refactoring barcode scanner code:

- Abstract the "controller" class (for future development)
- Break barcode scanning code out into multiple files
- Add CameraBarcodeController class (qr_code_scanner)

* Add await

* Make barcode scan delay configurable

* remove unused import

* Handle camera exceptions

* Improve sequencing for camera scanner

- Show loading overlay
- Prevent reload if view is no longer mounted

* Update docstring

* Update release notes

lib/barcode/tones.dart

@@ -0,0 +1,23 @@
+import "package:inventree/helpers.dart";
+import "package:inventree/preferences.dart";
+
+/*
+ * Play an audible 'success' alert to the user.
+ */
+Future<void> barcodeSuccessTone() async {
+
+  final bool en = await InvenTreeSettingsManager().getValue(INV_SOUNDS_BARCODE, true) as bool;
+
+  if (en) {
+    playAudioFile("sounds/barcode_scan.mp3");
+  }
+}
+
+Future <void> barcodeFailureTone() async {
+
+  final bool en = await InvenTreeSettingsManager().getValue(INV_SOUNDS_BARCODE, true) as bool;
+
+  if (en) {
+    playAudioFile("sounds/barcode_error.mp3");
+  }
+}