István Pásztor

Write helpful `__str__` and/or `__repr__` for the config wrapper classes (`ConfigJSONObject`, `ConfigJSONArray`, and `ConfigJSONValue`).

Based on the available info in `JSONConfigValueNotFoundError` it would be possible to produce more human friendly and easier to understand error messages.

Not too long but detailed enough docs for developers/library-hackers about the architecture/inner-working of this library.