Add autosave and restore from autosave new feature

[ianp5a]

New Feature Option to Autosave and Restore Scenes. Similar to other PC and mobile applications
Useage:

1. The application saves the current scene to an auto save path after every interaction.
2. At application start, the scene is loaded from the previous session autosave.
3. The user can close and open the app and continue working with no explicit file interactions
4. At application start, any autosave can be cleared using the current New Scene command
5. If the Scene had been also explicitly saved under a file name, this file and path is recorded in the autosave. So future explicit (CTRL-S) saves overwrite the defined/named file. The loaded autosave Scene may include changes since the last explicit save.

Benefits are to prevent accidental loss of work. Convenience for quick or temporary Scenes, reducing thinking about files and paths. Work in a similar, natural way to other apps with autosave. See Inkscape or mobile apps.