Add Support for using Behaviours with Mindville Insight custom fields

Behaviours don't consistently work with fields that have types from Riada's Insight plugin. If you try to, for example, hide the custom field:

def currentCf = getFieldById('my-insight-field-id')
currentCf.setHidden(true)

This will fail, and the browser console will display a message "Unrecognised backend ID".

Support for other plugins' custom field types is very limited in Behaviours, but enough users have asked about this to merit a new feature request.

Acceptance Criteria

• It's working for Jira, and as part of this story, it should be working for JSD
  • Older versions apparently work, and new versions don't work