Enable multiple order parameters

lib/api/client.dart

@@ -28,7 +28,7 @@ class Client {
         'Content-Type': 'application/json'
       };
 
-  Future<dynamic> get(String url, [Map<String, String> queryParameters]) {
+  Future<dynamic> get(String url, [Map<String, List<String>> queryParameters]) {
     // TODO: This could be moved to a seperate function
     var uri = Uri.parse('${this.base}$url');
     // Because these are all final values, we can't just add the queryParameters and must instead build a new Uri Object every time this method is called.

lib/api/task_implementation.dart

@@ -28,7 +28,7 @@ class TaskAPIService extends APIService implements TaskService {
   }
 
   @override
-  Future<List<Task>> getAll(int listId, [Map<String, String> queryParameters]) {
+  Future<List<Task>> getAll(int listId, [Map<String, List<String>> queryParameters]) {
     return client
         .get('/lists/$listId/tasks', queryParameters)
         .then((list) => convertList(list, (result) => Task.fromJson(result)));

lib/pages/list/list.dart

@@ -106,9 +106,9 @@ class _ListPageState extends State<ListPage> {
 
   Future<void> _loadTasksForPage(int page) {
     return VikunjaGlobal.of(context).taskService.getAll(_list.id, {
-      "sort_by": "done",
-      "order_by": "asc",
-      "page": page.toString()
+      "sort_by": ["done", "id"],
+      "order_by": ["asc", "desc"],
+      "page": [page.toString()]
     }).then((tasks) {
       setState(() {
         _loading = false;

lib/service/mocked_services.dart

@@ -137,7 +137,7 @@ class MockedTaskService implements TaskService {
   }
 
   @override
-  Future<List<Task>> getAll(int listId, [Map<String, String> queryParameters]) {
+  Future<List<Task>> getAll(int listId, [Map<String, List<String>> queryParameters]) {
     return Future.value(_tasks.values.toList());
   }
 

lib/service/services.dart

@@ -26,7 +26,7 @@ abstract class TaskService {
   Future<Task> update(Task task);
   Future delete(int taskId);
   Future<Task> add(int listId, Task task);
-  Future<List<Task>> getAll(int listId, [Map<String, String> queryParameters]);
+  Future<List<Task>> getAll(int listId, [Map<String, List<String>> queryParameters]);
   // TODO: Avoid having to add this to each abstract class
   int get maxPages;
 }