Fancy Save Picker + Autosave Feature

[NQNStudios]

Add autosaves - Fix #275. Each manually created party can have a rolling buffer of autosaves and these saves happen when a variety of triggers occur that seem sensible to me:

• Resting/Long Waiting without interruption
• Entering Town/Leaving Town
• Finishing outdoor combat
• Eating when you have enough food

Can you think of any other potential triggers?

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This also adds a fancy save-game picker that handles loading and overwriting, as well as a nice front-end for autosaves.

This will serve as a safeguard against #327 for Linux users.

It might be incomplete if it's currently possible to get a party member with a custom graphic or monster graphic, but I wasn't able to make one by normal means so I didn't finish/test rendering those types of PC graphics in the picker. I commented in the code where that would go, and also added a TODO on the startup menu rendering those PC graphic types because it looks wrong to me.

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TODO

• Preference for using the new file picker or not
• make sure the picker doesn't break replays
• (top priority) the picker is slow to load because it loads parties 3 or 4 at a time and some of them load very slowly because of seemingly unrelated errors (Windows version printing tons of parse exceptions)
• Preference for default save folder
• If the player manually uses the OS file browser to select a save not in the configured save dir, ask if they want to move it in
• with a "don't ask again" option
• prompt to change saveDir when saving outside of saveDir through OS file browser
• with a "don't ask again" option
• Linux zenity check can happen silently and warn and/or disable the the File Browser button if fails, instead of exiting forcefully

Autosave preferences

• Global on/off preference
• max number autosaves
• on safe rest
• on town wait
• on enter town
• on leave town
• on party eats
• on outdoor combat finish