Adds the ability for single level grouping to the Grid.

Default getSclass(): the same as grid's sclass.

<?xml version="1.0" encoding="UTF-8"?>
<zk>
    Grid support Groupfoot in Group    

    <grid id="grid">    
        <columns id="h" sizable="true">        
            <column id="col1" label="Type"/>            
            <column id="col2" label="Content"/>            
        </columns>        
        <rows id="rows">        
            <group id="gp1">            
            <label value="Group1: (gp1)"/>            
            <label value="Group1:"/>            
            </group>            
            <row>            
                <label value="File:"/>                
                <label value="File:"/>                
            </row>            
            <row id="row1">            
                <label value="Type:"/>                
                <hbox>                
                    <listbox rows="1" mold="select">                    
                        <listitem label="Java Files,(*.java)"/>                        
                        <listitem label="All Files,(*.*)"/>                        
                    </listbox>                    
                    <button label="Browse..."/>                    
                </hbox>                
            </row>            
            <groupfoot>            
                <label value="2 Java Files"/>                
                <label value="10 Files"/>                
            </groupfoot>            
            <group id="gp2" label="Group 2 (gp2)" onOpen='alert("Group is open: "+self.open);'/>            
            <row>            
                <label value="Options:"/>                
                <label value="Options:"/>                
            </row>            
                <groupfoot>                
                <label value="2 Options"/>                
                <label value="10 Options"/>                
            </groupfoot>            
        </rows>        
    </grid>    
</zk>