Add extra workflow input annotations

[innovate-invent]

I need to be able to pass extra values to my frontend that informs how the input should be handled.
Currently I am passing json in the annotation:

{ "annotation": "Select data to analyze.", "order":0, "validator":"(selection && selection.length > 1)?'':'Please select at least two datasets'" }

A dedicated kv map of extra values or some sort of fields would be nice.

It would be good to add an "order" property outside of the arbitrary values to specify a number to sort the inputs on when displaying to the user for the Galaxy UI.