Added sorting to all columns at users and groups at system window's groups tab

ubl-settings-usergroups-system.glade

@@ -380,6 +380,7 @@ without activity</property>
                         <property name="sizing">fixed</property>
                         <property name="min-width">50</property>
                         <property name="title" translatable="yes">Group</property>
+                        <property name="sort-column-id">1</property>
                         <child>
                           <object class="GtkCellRendererText">
                             <property name="wrap-width">150</property>
@@ -395,6 +396,7 @@ without activity</property>
                         <property name="min-width">50</property>
                         <property name="title" translatable="yes">Group
 users</property>
+                        <property name="sort-column-id">2</property>
                         <child>
                           <object class="GtkCellRendererText"/>
                           <attributes>