feat(docparser): support jsonapi tags

[rlespinasse]

The specification format is available at http://jsonapi.org/format/ Support jsonapi tags during the generation phase.

Support status of top-level members

• data is supported,
• includes is supported (skip it with --without-jsonapi-includes),
• errors objects can be handle by json tags (with an ErrorObject and an ErrorsPayload components).
• meta, jsonapi, links are not supported.

For a given Foo object, the use of jsonapi tags will generated all components needed to represent the jsonapi format of this object.

• Foo as a resource object
• FooAttributes
• FooCollection: as an array of resource objects
• FooData
• FooIdentifier: as a resource identifier object
• FooIdentifierCollection: as an array of resource identifier objects
• FooIdentifierData
• FooRelationships

Others contents needed for this support

• make test will run openapi-parser against various datasets,
• Support of string attribute in a json tag (dataset/jsontags),
• Fix a typo in yaml tag of the server struct,
• Parse json, jsonapi, and validate tags separately,
• Field Items from Schema now support a single string value OR a array of Schema,
• All warnings during file parsing became fatal to the openapi file generation.

[rlespinasse]

Others information

The content of this pull-request is currently used at my previous work. A first code review / pair programming on some parts have being done by @denouche (thanks to him)

Related to #18

[denouche]

Can I close this one @rlespinasse ?