Get default value from URL

[jkrehm]

Use case: pre-populating form inputs with results from an API endpoint (external to Form.io).

I know the code does not currently support this, so what I'm wondering is if (a) you are interested in this type of functionality (I know I am) and (b) if you have any ideas on the best way to implement. If you already have an idea but don't want to spend the development time, please let me know what approach you would like to take. I'm happy to take a crack at it and submit a PR.

The defaultValue functionality does not appear to currently have anything like a setValue function that can be used by a callback/promise. I think to make it possible, such a thing would have to exist.

Thoughts?