Add enum to Java docs

* Parameter enum values
* Inner enum class (model property)
* Outer enum class (enum model/definition)

samples/client/petstore/java/okhttp-gson/docs/Animal.md

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+
+# Animal
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**className** | **String** |  | 
+
+
+