jackson210

Support for Jackson-powered parsing and printing for circe.

Note that not all guarantees that hold for Jawn-based parsing and the default printer will hold for the Jackson-based versions. Jackson's handling of numbers in particular differs significantly: it doesn't distinguish positive and negative zeros, it may truncate large JSON numbers or simply fail to parse them, it may print large numbers as strings, etc.

The implementation is ported with minimal changes from Play JSON.