Key-value pair in additional properties retains order when edited

[aerfio]

Reasons for making this change

When you change key it shows on the bottom of the list, instead of keeping its place, keeping the order of key-value pairs.

If this is related to existing tickets, include links to them as well.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
  • If I'm adding a new section, I've updated the Table of Content
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
  • I've run npm run cs-format on my branch to conform my code to prettier coding style
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

Solves two things of #1099

[aerfio]

@glasserc @edi9999 Any comment on this and/or related issue?

[edi9999]

Can you add a test case in the same form as https://github.com/mozilla-services/react-jsonschema-form/blob/master/test/ObjectField_test.js#L582 that fails before your patch, and succeeds afterwards ?

[aerfio]

@edi9999 Done, those tests fail on master and succeed here

[edi9999]

Great , merging !

[aerfio]

@edi9999 When do you guys plan to realease 1.0.7? Do you have it scheduled?