Ability to Save Current State to File

[teubert]

Suggestion of @jason-watkins from v1.0 release review.

It would be nice to have a feature that allows users to save the current state of the system (all sessions) to a file to be restored. The point is to be able to share a single state between researchers or to restore to a known point before trying different actions.

D.o.D.

• Ability to save all sessions implemented
• Ability to restore from save implemented
• Tests exist
• Added to documentation
• Added to release notes for v1.1