Add v3 ListResources support to gcf am.
Add v3 ListResources support to gcf am.

Remove the slice urn functionality of the v2 ListResources, and add a
helpful message if the client passes the slice_urn option.

tcmitchell/geni-tools,plantigrade/geni-tools,GENI-NSF/gram,tcmitchell/geni-tools,ahelsing/geni-tools,GENI-NSF/gram,plantigrade/geni-tools,ahelsing/geni-tools,GENI-NSF/gram