Add Export Cohort Function to Apprentice Levy System

Issue #74 resolved
Emil Reisser-Weston
created an issue

Should select users from a list to add to a cohort.

Use the same functionality as Assign Learning but instead "Assign Apprenticeships"

Need to design for upload to goverment website - once 8.4 version released. See https://vimeo.com/209222739 for preview