Adding option to save and load state by mtime

Load by mtime: load last state is expanded from 1 to 8 actions, for newest to oldest state

Save by mtime: overwrite the oldest state (or use an empty slot if available). This wait for a save to be written (before allowing another state to be saved) because it must reliably know which files are on disk

Adding remaining hardcoded state keys to hotkey dialog

Adding a program exit hotkey