Disallow edits of snapshot values in composite snapshot view

Author: georgweiss

app/save-and-restore/app/src/main/java/org/phoebus/applications/saveandrestore/ui/snapshot/SnapshotController.java

@@ -894,6 +894,7 @@ private void showLoggingError(String cause) {
      */
     public void loadSnapshot(Node snapshotNode) {
         disabledUi.set(true);
+        storedValueColumn.editableProperty().set(snapshotNode.getNodeType().equals(NodeType.SNAPSHOT));
         JobManager.schedule("Load snapshot items", monitor -> {
             try {
                 this.snapshot = getSnapshotFromService(snapshotNode);