Choose folder to store data

All persistent data is currently stored on a local, pretty much hidden, folder. It's Godot engine default folder but it would be very useful to be able to choose a specific folder.

This folder would be set at first run or would be edited through some settings latter.

It would be useful for:

• backup data
• share data in a shared folder on a local network (using samba for instance)
• sync data across multiple devices