Session record

Problem to solve

Actually every session related data are saved into the memory. The ony way to save data is to make a blend save but it is not possible through a headless server.

Proposal

Add a replication graph backup system to the replication package.

Further details

The goals would be to allow:

1. Périodic backup save
2. Restore the session on the backup (from blender or directly on the headless server)
3. Add debugging tools to display backups history