Don't use inline <style> in a <div>, but in an external <link>.

This fixes:

    Using nu validator to parse the view "TestPage_viewTestReport" (from erp5_run_my_doc bt) with warnings displayed :
    Error: line 581 column 23 : Element “style” not allowed as child of element “div” in this context. (Suppressing further errors from this subtree.): "><div  >
    <style type="text/css">
    body,