gcgetmemberships should allow calls by folder or scope

/**

 * validate this call

 */

 private void validate() {

 if (GrouperClientUtils.length(this.groupNames) == 0

 && GrouperClientUtils.length(this.groupUuids) == 0

 && GrouperClientUtils.length(this.membershipIds) == 0

 && GrouperClientUtils.length(this.wsSubjectLookups) == 0) {

 throw new RuntimeException("Group name or uuid or subject lookup or membership id is required: " + this);

 }

 }