AG-1053 Tidy react examples, make more idiomatic

src-examples/simpleReduxExample/gridDataReducer.jsx

@@ -0,0 +1,16 @@
+export default (state = {rowData: [], rowSelection: []}, action) => {
+    switch (action.type) {
+        case 'ROW_DATA_CHANGED':
+            return {
+                ...state,
+                rowData: action.rowData,
+            };
+        case 'ROW_SELECTION_CHANGED':
+            return {
+                ...state,
+                rowSelection: action.rowSelection,
+            };
+        default:
+            return state;
+    }
+};