Add a visibility option to nodes
Parts of the knowledge graph should not be visible to the user. We therefore need options to not show certain nodes. Currently two options may be interesting:
- Give each node a date after which it will be visible
- Give each node an additional category for which visibility can be set globally through the editor.
This issue may require a more complex design for #7 (closed). We may need to save each node and link individually in the database.