Undo operation 'delete node'
(Since version 0.0.9)
The 'delete node' operation can be undone if you have not changed a site tree.
The 'delete node' operation can be undone if you have not changed a site tree.
I.e. you cannot undo operation 'delete node' if you
1. add another node
2. delete another node
3. start a new site (create new .qxt file)
4. open another site (.qxt file)
1. add another node
2. delete another node
3. start a new site (create new .qxt file)
4. open another site (.qxt file)
