Implement saving/loading of persistent values to configure multiple views

Desired workflow: The user programmatically configures several "views" of their data, each of which corresponds to a different collection of settings (stuff which is enabled, etc). The user wants to quickly switch between these views without clicking a bunch.

How to get there: We could get this fairly easily by leveraging the persistent value caches. Work items would be:

• define a serialization format for persistent values (in-memory for now)
• add a storeConfiguration() function or something, which saves the state of all persistent values to an internal list
• add a loadConfiguration() function which restores persistent values
• buttons in the GUI, etc

This has significant overlap with things we would want to do regardless to enable serialization more broadly.

Commencez par lire include/polyscope/persistent_value.h et par suivre la manière dont les valeurs persistantes sont créées et consultées. Définissez le format de sérialisation en mémoire et la portée de l’état stocké avant d’implémenter la sauvegarde et le chargement de la configuration ; n’envisagez les boutons de l’GUI qu’une fois le comportement principal spécifié et testable.