Improve Array Input in JSON Forms

[dyaffe]

Problem
Currently inputting arrays in JSON forms is tedious and messy. Using it isn't obvious and is quite error prone.

The easiest way to make it simpler would be to change it to a bulk input select where a user inputs a comma separated list.

If that's hard, then having the ability to re-order would be nice.

[travjenkins]

We have to be specific with the forms. So I think this would be for arrays of strings or numbers.

[travjenkins]

A specific use case is headers for CSV docs. This makes setting the headers very hard and would like to be able to paste in a comma separated list.

[travjenkins]

blocked by #809

[travjenkins]

The main reason for pushing this was handling headers for connectors. This is now handled better automagically so this is less important. Removing from the backlog for now.