Option to use LinkedHashMap instead of HashMap to preserve additionalProperties keys order

[x1diablo]

It's quite annoying that additionalProperties values lose their initial array order when json is parsed.
Since I use the same schema classes to generate json after tweaking, I can't sort them too.

I guess it will be easy to add an option to generate LinkedHashMap instead of HashMap for additionalProperties field.

[jdimeo]

This is an easy change, and I'm not even sure it should be configurable- I think it should be the new default behavior:
jdimeo@de79bf0

[hupfdule]

This is an easy change, and I'm not even sure it should be configurable- I think it should be the new default behavior

I think the same way.

Do you mind creating a PR for your change?

[jdimeo]

OK I did: #1397

[joelittlejohn]

Closed by #1397.