Project code support (#336)

* Determine if project codes are supported

* Add helpers for boolean functions

* Adds helper methods for generic "model" class

- Will allow us to do some good refactoring

* Refactor the refactor

* Add debug support and getMap function

* Major refactoring for model data accessors

* Handle null values

* Add sentry reporting if key is used incorrectly

* Fix typo

* Refactor createFromJson function

* Add model for ProjectCode

* Display and edit project code for purchase orders

lib/api_form.dart

@@ -15,6 +15,7 @@ import "package:inventree/l10.dart";
 
 import "package:inventree/inventree/company.dart";
 import "package:inventree/inventree/part.dart";
+import "package:inventree/inventree/project_code.dart";
 import "package:inventree/inventree/sentry.dart";
 import "package:inventree/inventree/stock.dart";
 
@@ -667,6 +668,13 @@ class APIFormField {
             height: 40
           )
         );
+      case "projectcode":
+        var project_code = InvenTreeProjectCode.fromJson(data);
+        return ListTile(
+          title: Text(project_code.code),
+          subtitle: Text(project_code.description),
+          leading: FaIcon(FontAwesomeIcons.list)
+        );
       default:
         return ListTile(
           title: Text(