I've updated the deserialization to provide a list of suggestions for unknown field names. This uses the Fastenshtein library to calculate the edit distance between the field name entered by a user and the possible fields.

I've chosen to return fields if they have an edit distance less than 3. This is fairly arbitrary and just based on some simple testing. I wanted to provide suggestions, but not provide ones that were completely different to the name entered.

Also:

- Updated the V1Deserializer to use the `Map()` syntax for mapping rather than doing everything manually. The main reason for this was so that the fields are added as suggestions, although it also removes some unnecessary code.
- Altered MetricsDeclarationProvider to not set the defaults if validating the metrics fails. The reason I've done this is that if the metric defaults couldn't be deserialized, we end up with a NullReferenceException.

Fixes tomkerkhove#1105