Add mappings to/from intermediate objects for NoSQL support

[sjohnr]

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This is a draft solution for supporting NoSQL databases. It uses intermediary objects (currently called "Resources", but open to better names) to simplify a transformation to/from JSON. The intermediary objects support full serialization to JSON with the use of the OAuth2AuthorizationServerJackson2Module. Supports the following:

• Handles iterating/mapping supported token types, removing the need for applications to do this
• Converts enumerated types to/from strings with support for "custom" types
• Converts authorities to/from strings
• Supports custom settings values

Issue gh-558

[HKMV]

Hello, there is no normal merging

[sjohnr]

Closing for now. May re-open when we revisit this.