Graph Snapshots

[allantokuda]

Add a "Snapshot" button (after the New button) that saves a read-only copy of the current state of the graph to the server. The snapshot can be viewed at /snapshots/:snapshot_id and looks about the same as the graph editor, but is not editable: it has has no toolbar and does not respond to click or keyboard events. It shows the save date & time in the upper right. The user is redirected to the snapshot upon creation. The snapshot_id is a long random number like the existing graph_id.

The intent is to allow the author to send a link to others, without the recipients being able to edit the graph.