KEYCLOAK-2154 Added Group mapper for LDAP. LDAP mappers improvements and fixes

examples/providers/federation-provider/src/main/java/org/keycloak/examples/federation/properties/BasePropertiesFederationProvider.java

@@ -96,6 +96,11 @@ public abstract class BasePropertiesFederationProvider implements UserFederation
         return Collections.emptyList();
     }
 
+    @Override
+    public List<UserModel> getGroupMembers(RealmModel realm, GroupModel group, int firstResult, int maxResults) {
+        return Collections.emptyList();
+    }
+
     @Override
     public void preRemove(RealmModel realm) {
        // complete  We don't care about the realm being removed