- fixes the uninitialized problem
- does not set values to None if they are not updated while others are
- restores previous config if there is an error in the new one
(+tests)

Also added a few TODO's, which are needed, but not as urgently as these (eg take defaults from spec, which would require more changes than i want to do right now, as does making a separate class for storing these values so they don't all have to be backed up when applying a new config)