Update multi-select choice list control creation

[doneill]

Creating CHOICE_LIST contols is not properly distinguishing between single-select and multi-select choice lists. Array-type choice lists with inputType: LIST are getting format: radio which tells JSONForms to use a single-select renderer, but multi: true was conflicting, causing renderer confusion and potential client crashes

Action:

• Differentiate single vs multi-select choice lists and use checkbox for multi

Expectation:

• Multi-select choice lists generate correct UISchema to effectively route to a MultiselectPickerRenderer instead of an UnknownRenderer

[doneill]

Fixed with #27