Add config options to restrict membership export

In order to prevent users from downloading a list of all employees, etc., have some way to restrict the export functionality.

Options?
1) Restrict by object type
2) Exclude based on an attribute (create a built-in one, rather than making everyone make one up)
3) Restrict by regular expression patterns:

uiV2.group.exportDisallowedPattern.0 = ^ref:affiliation:.*