Toggle between expanded/collapsed state when clicking on
the group.
@private
function(view, rowElement, groupName, e) {
        var me = this,
            groupCache = me.groupCache,
            groupIsCollapsed = !me.isExpanded(groupName),
            g;

        if (me.collapsible) {

            // CTRL means collapse all others
            if (e.ctrlKey) {
                Ext.suspendLayouts();
                for (g in groupCache) {
                    if (g === groupName) {
                        if (groupIsCollapsed) {
                            me.expand(groupName);
                        }
                    } else {
                        me.doCollapseExpand(true, g, false);
                    }
                }
                Ext.resumeLayouts(true);
                return;
            }

            if (groupIsCollapsed) {
               me.expand(groupName);
            } else {
                me.collapse(groupName);
            }
        }
    }