Java, property getters added to map output class

[spacether]

Java, improves map output type

• input types used in SomeSchema.validate
• input types used in SomeSchemaMap.of
• output types used in SomeSchema.getMapOutputInstance
• adds accessor methods for validly named properties + required properties
• adds accessor method getAdditionalProperty

Notes:
If an optional key/additional property key is not present an exception is thrown

• this was done because null is not an allowed value for an unset key. Null may be set as a value in a required or optional property, it does not mean unset in this context

PR checklist

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  ./bin/utils/export_docs_generators.sh
  

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