Support additional Custom Fields on JSD Widget

Current Behavior.

JIRA Service Desk Widget does not display a few custom field types, such as URL, Select Lists (cascading), Labels, Date. Including an unsupported field type on the request type form will throw the following message on the Widget configuration:

If the Widget is embedded on a website:

• Having an unsupported field on the default request type will cause the widget to fail to load (help button won't show)
• If request type search is turned on, having an unsupported field on one of the search results will cause an error to be shown when searching

Desired Behavior.

As a Service Desk admin, I would like to be able to include those fields on the widget form.

Currently supported fields

• System fields: Summary, Description, Priority, Components, Fix Version/s, Attachments
• Custom fields: Single & multi line text, Single & multi select, Radio, Checkbox