group permit to groups navigation elements to the left or right side of a menubar.
<group expand="true|false">
where:
The first group will be at the left and the search form at the right
<menubar>
<group expand="true">
[[#|Menubar]]
<dropdown name="Nav Menu">
[[#|Menubar]]
[[#|DropDown]]
[[#|Search]]
</dropdown>
</group>
<search>
</menubar>