Show a list of members that are part of a given membergroup.

• Called by ?action=membergroups;sa=members;group=x
• Requires the manage_membergroups permission.
• Uses the group_members sub template of ManageMembergroups.
• Allows admin to add and remove members from the selected membergroup.
• Allows sorting on several columns.
• Redirects to itself.
• Was located in ManageMembers.php in 1.0.x
• Moved to Groups.php in 2.0