Merge branch '33-forbid-delete-value-in-fixed-cell' into 'master'

Resolve "Forbid delete value in fixed cell"

Closes #33

See merge request !28

android/gradle.properties

 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=true
-app.versionName=0.0.25
-app.versionCode=25
+app.versionName=0.0.26
+app.versionCode=26

fastlane/metadata/android/en-US/changelogs/26.txt

+Fix forbid change value of fixed initial cell

fastlane/metadata/android/fr-FR/changelogs/26.txt

+Correction sur l'interdiction de modification de la valeur d'une cellule initiale

lib/provider/data.dart

@@ -124,7 +124,9 @@ class Data extends ChangeNotifier {
   }
 
   updateCellValue(int col, int row, int value) {
-    _cells[row][col].value = value;
+    if (!_cells[row][col].isFixed) {
+      _cells[row][col].value = value;
+    }
     notifyListeners();
   }