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/stock/location_list.dart

@@ -0,0 +1,99 @@
+import "package:flutter/material.dart";
+
+import "package:inventree/inventree/model.dart";
+import "package:inventree/inventree/stock.dart";
+import "package:inventree/widget/stock/location_display.dart";
+import "package:inventree/widget/paginator.dart";
+
+import "package:inventree/widget/refreshable_state.dart";
+import "package:inventree/l10.dart";
+
+
+class StockLocationList extends StatefulWidget {
+
+  const StockLocationList(this.filters);
+
+  final Map<String, String> filters;
+
+  @override
+  _StockLocationListState createState() => _StockLocationListState(filters);
+}
+
+
+class _StockLocationListState extends RefreshableState<StockLocationList> {
+
+  _StockLocationListState(this.filters);
+
+  final Map<String, String> filters;
+
+  @override
+  String getAppBarTitle() => L10().stockLocations;
+
+  @override
+  Widget getBody(BuildContext context) {
+    return PaginatedStockLocationList(filters);
+  }
+}
+
+
+class PaginatedStockLocationList extends PaginatedSearchWidget {
+
+  const PaginatedStockLocationList(Map<String, String> filters, {String title = ""}) : super(filters: filters, title: title);
+
+  @override
+  String get searchTitle => title.isNotEmpty ? title : L10().stockLocations;
+
+  @override
+  _PaginatedStockLocationListState createState() => _PaginatedStockLocationListState();
+}
+
+
+class _PaginatedStockLocationListState extends PaginatedSearchState<PaginatedStockLocationList> {
+
+  _PaginatedStockLocationListState() : super();
+
+  @override
+  Map<String, String> get orderingOptions => {
+    "name": L10().name,
+    "items": L10().stockItems,
+    "level": L10().level,
+  };
+
+  @override
+  Map<String, Map<String, dynamic>> get filterOptions => {
+    "cascade": {
+      "label": L10().includeSublocations,
+      "help_text": L10().includeSublocationsDetail,
+      "tristate": false,
+    }
+  };
+
+  @override
+  Future<InvenTreePageResponse?> requestPage(int limit, int offset, Map<String, String> params) async {
+
+    final page = await InvenTreeStockLocation().listPaginated(limit, offset, filters: params);
+
+    return page;
+  }
+
+  @override
+  Widget buildItem(BuildContext context, InvenTreeModel model) {
+
+    InvenTreeStockLocation location = model as InvenTreeStockLocation;
+
+    return ListTile(
+      title: Text(location.name),
+      subtitle: Text(location.pathstring),
+      trailing: Text("${location.itemcount}"),
+      leading: location.customIcon,
+      onTap: () {
+        Navigator.push(
+          context,
+          MaterialPageRoute(
+            builder: (context) => LocationDisplayWidget(location)
+          )
+        );
+      },
+    );
+  }
+}