Handle exceptions for specific config keys more gracefully when loading configs for mods

[Nytra]

Currently if a single key in the mod config throws an error on loading, it results in the entire config being reset to default and a backup file being created, rather than only resetting the key that threw the error.

I have run into this when changing enum value names used for config keys.

Related discussion: neos-modding-group/NeosModLoader#100

The code that does this is in ModConfiguration.LoadConfigForMod method.