[BUG] [core] CodegenConfigurator not applying all GeneratorSettings

Created by: chameleon82

Bug Report Checklist

I trying to apply custom GeneratorSettings, but get only default ones. For example with "scala-akka" template i got next:

          CodegenConfigurator configurator = new CodegenConfigurator()
          configurator.setGeneratorName("scala-akka")
          configurator.setPackageName("some.package")
          configurator.setApiPackage("some.package.api")
          configurator.setInvokerPackage("some.package.core")
          configurator.setModelPackage("some.package.model")

          ClientOptInput clientOptOutput = configurator.toClientOptInput

and the result is present with default values instead of defined explicitly

          clientOptOutput.getPackageName // this property not present at all
          clientOptOutput.getApiPackage = "org.openapitools.client.api"
          clientOptOutput.getInvokerPackage ="org.openapitools.client.core"
          clientOptOutput.getModelPackage = "org.openapitools.client.model"

Seems code can be improved here: https://github.com/OpenAPITools/openapi-generator/blob/c08e80f49b806de169f133e177be08b3e2bafa46/modules/openapi-generator/src/main/java/org/openapitools/codegen/config/CodegenConfigurator.java#L532

Next step to generate files is (which is obviously generating un-expecting result):

    DefaultGenerator codeGenerator = new DefaultGenerator
    codeGenerator.opts(opts).generate()

Should we cover those properties in CodegenConfigurator or there is another way to solve it?

Upd: Those properties converted to additionalProperties. Is it make sense to have those properties available for DefaultCodegen as a class properties or any specific reason to keep it in additionalProperties?

@jimschubert (2017/09) ❤️, @wing328 , @Helmsdown , @jmini