Groups UI: "member" column no longer sortable
Groups UI: "member" column no longer sortable

Since group membership is calculated on the fly (rather than stored as a
proprty of an ExplicitGroup), sorting is awkward. Also it's unclear to
the user: are we sorting by number of users? groups? sum of both?

Closes #2388

ekoi/DANS-DVN-4.6.1,ekoi/DANS-DVN-4.6.1,bmckinney/dataverse-canonical,bmckinney/dataverse-canonical,bmckinney/dataverse-canonical,quarian/dataverse,majorseitan/dataverse,ekoi/DANS-DVN-4.6.1,majorseitan/dataverse,leeper/dataverse-1,majorseitan/dataverse,ekoi/DANS-DVN-4.6.1,JayanthyChengan/dataverse,majorseitan/dataverse,majorseitan/dataverse,leeper/dataverse-1,quarian/dataverse,JayanthyChengan/dataverse,bmckinney/dataverse-canonical,leeper/dataverse-1,jacksonokuhn/dataverse,quarian/dataverse,quarian/dataverse,leeper/dataverse-1,quarian/dataverse,JayanthyChengan/dataverse,bmckinney/dataverse-canonical,bmckinney/dataverse-canonical,quarian/dataverse,jacksonokuhn/dataverse,leeper/dataverse-1,jacksonokuhn/dataverse,jacksonokuhn/dataverse,majorseitan/dataverse,ekoi/DANS-DVN-4.6.1,bmckinney/dataverse-canonical,jacksonokuhn/dataverse,quarian/dataverse,JayanthyChengan/dataverse,majorseitan/dataverse,leeper/dataverse-1,ekoi/DANS-DVN-4.6.1,leeper/dataverse-1,bmckinney/dataverse-canonical,JayanthyChengan/dataverse,majorseitan/dataverse,leeper/dataverse-1,JayanthyChengan/dataverse,ekoi/DANS-DVN-4.6.1,JayanthyChengan/dataverse,jacksonokuhn/dataverse,jacksonokuhn/dataverse,ekoi/DANS-DVN-4.6.1,JayanthyChengan/dataverse,quarian/dataverse,jacksonokuhn/dataverse