Barcode scanner updates (#562)

* Add BUILDING.md

* Replace scaning library

- Out with qr_code_scanner
- In with flutter_zxing

* Update specs for jdk / kotlin / gradle

- NFI what this all means?

* Refactor barcode scanning widget

* Refactor barcode overlay

* Add handlers

* Update release notes

* Fix AppBar color

* Enhance attachment widget

* remove unused import

* Improved icon

* Select theme from main drawer

lib/settings/select_server.dart

@@ -266,6 +266,7 @@ class _InvenTreeSelectServerState extends State<InvenTreeSelectServerWidget> {
       key: _loginKey,
       appBar: AppBar(
         title: Text(L10().profileSelect),
+        backgroundColor: COLOR_APP_BAR,
         actions: [
           IconButton(
             icon: Icon(TablerIcons.circle_plus),