Sales order support (#438)

* Add new models for SalesOrder

- Create generic Order and OrderLine models with common functionality

* Refactor

- Move some widgets around
- Cleanup directory structure

* Add link to home screen and nav drawer

* Add SalesOrder list widget

* Linting fixes

* Fix string

* Refactor PurchaseOrderDetailWidget

* Tweaks to existing code

* linting

* Fixes for drawer widget

* Add "detail" page for SalesOrder

* Add more tiles to SalesOrder detail

* Allow editing of salesorder

* add list filters for sales orders

* Display list of line items

* Customer updates

- Display customer icon on home screen
- Fetch sales orders for customer detail page

* Cleanup company detail view

* Create new sales order from list

* Stricter typing for formFields method

* Create new PurchaseOrder and SalesOrder from company deatil

* Status code updates

- Add function for name comparison
- Remove hard-coded values

* Update view permission checks for home widget

* Add ability to manually add SalesOrderLineItem

* Add nice progress bar widgets

* Display detail view for sales order line item

* edit SalesOrderLineItem

* Fix unused import

* Hide "shipped items" tab

- Will be added in a future update

lib/widget/company/company_list.dart

@@ -0,0 +1,83 @@
+
+import "package:flutter/material.dart";
+
+import "package:inventree/api.dart";
+
+import "package:inventree/inventree/company.dart";
+import "package:inventree/inventree/model.dart";
+
+import "package:inventree/widget/paginator.dart";
+import "package:inventree/widget/refreshable_state.dart";
+import "package:inventree/widget/company/company_detail.dart";
+
+
+/*
+ * Widget for displaying a filterable list of Company instances
+ */
+class CompanyListWidget extends StatefulWidget {
+
+  const CompanyListWidget(this.title, this.filters, {Key? key}) : super(key: key);
+
+  final String title;
+
+  final Map<String, String> filters;
+
+  @override
+  _CompanyListWidgetState createState() => _CompanyListWidgetState();
+}
+
+
+class _CompanyListWidgetState extends RefreshableState<CompanyListWidget> {
+
+  _CompanyListWidgetState();
+
+  @override
+  String getAppBarTitle() => widget.title;
+
+  @override
+  Widget getBody(BuildContext context) {
+    return PaginatedCompanyList(widget.title, widget.filters);
+  }
+
+}
+
+class PaginatedCompanyList extends PaginatedSearchWidget {
+
+  const PaginatedCompanyList(this.companyTitle, Map<String, String> filters) : super(filters: filters);
+
+  final String companyTitle;
+
+  @override
+  String get searchTitle => companyTitle;
+
+  @override
+  _CompanyListState createState() => _CompanyListState();
+}
+
+class _CompanyListState extends PaginatedSearchState<PaginatedCompanyList> {
+
+  _CompanyListState() : super();
+
+  @override
+  Future<InvenTreePageResponse?> requestPage(int limit, int offset, Map<String, String> params) async {
+
+    final page = await InvenTreeCompany().listPaginated(limit, offset, filters: params);
+
+    return page;
+  }
+
+  @override
+  Widget buildItem(BuildContext context, InvenTreeModel model) {
+
+    InvenTreeCompany company = model as InvenTreeCompany;
+
+    return ListTile(
+      title: Text(company.name),
+      subtitle: Text(company.description),
+      leading: InvenTreeAPI().getThumbnail(company.image),
+      onTap: () async {
+        Navigator.push(context, MaterialPageRoute(builder: (context) => CompanyDetailWidget(company)));
+      },
+    );
+  }
+}