You can now use the web API server for groups to update
group members by uploading a CSV file to update membership

The new page is below, and gives all the details about the format
/admin/groups/uploadmemberscsv.php

Change-Id: I0351b21a933646d7e528852680f457ac6ea93596
Signed-off-by: Hugh Davenport <hugh@catalyst.net.nz>