Updated converter to allow the mixing of ApiModel annotations and JsonTypeInfo/JsonSubTypes annotations

Previously if you defined ApiModel with only a description, the discriminator and subTypes info would not be read from the Jackson annotations.
Return sub models if a base model referenced as dependent field

Previously, sub type models were only returned for top level models. For our purposes, I've updated this to return the sub types for all the dependent models
Models that are referenced in a Map value should be returned as a required model

If we have a Model A that has the field myMap[String,B] and we attempt to read all the dependencies of model A, then B does not get returned. I've fixed this to now return B...
Merge branch 'polymorphic-fixes' of https://github.com/jknova/swagger-core into polymorphic-fixes