Eliminate vets.gov-isms in form submit and file upload

[dmethvin-gov]

There are still quite a few things that depend on server behavior specific to vets.gov like the use of req.setRequestHeader('X-Key-Inflection', 'camel') in actions.js that expects the use of particular Rails middleware. Since servers and their configurations are so different this might be a good place to just have the app pass us a callback in formConfig. We pass it the formData and they use to submit the form, serializing it whatever way they want (JSON, XML, form-urlencoded). The same goes for file uploads.

[dmethvin-gov]

Adding the va-growable-* classes in m-schemaform.scss. I suppose these might just need to be renamed to be generic but they may be defining some style we want to modify.

[jcmeloni-usds]

@dmethvin-gov Confirming this is still ongoing -- correct?

[dmethvin-gov]

Yes, I'll be making some changes once the new router lands.

[jcmeloni-usds]

Ok, moved to phase 2 and the 2.0.0-alpha1 milestone

[annekainicUSDS]

Another thing to add here: the "Submit again" button that only appears in dev and staging, we want to remove that now.

[dmethvin-gov]

Adding the rework of stringifyFormReplacer from #259, which currently has special case processing for various widgets.