parse PROVIDED_IN_ROOT correctly

[manbearwiz]

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• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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Description of the PR

When running the codegen integration in SwaggerHub, if you check the "providedInRoot" option in Codegen options, the integration fails saying

The 'Azure DevOps Services' plugin failed with the following error: java.lang.Boolean cannot be cast to java.lang.String

This change fixes this by parsing PROVIDED_IN_ROOT the same way as other booleans, Boolean.parseBoolean(additionalProperties.get(KEY).toString()). It also changes the default to true on angular versions ^6.0.0.

See also OpenAPITools/openapi-generator#3558