added sent and id column again for add_cam_main

id checks if entry already exists. sent says if the entry is already
sent to the db

lib/methods/excursion_db_helper.dart

@@ -65,10 +65,10 @@ class ExcursionDBHelper implements IDb{
   }
 
   @override
-  Future<void> updateMainEntry(Map<String, String> excursion) async {
+  Future<int> updateMainEntry(Map<String, String> excursion) async {
     var excursionDBClient = await dB;
 
-    await excursionDBClient
+    return await excursionDBClient
         .update('excursion', excursion, where: "ID = ?", whereArgs: [excursion['ID']]);
   }