Determines whether 'render-widget-body- wraps the
body in a form. This behavior is occassionally useful (in case of the
datagrid), and occassionally harmful (in case of the datalist). It is
useful when selection is allowed and selection controls must be in the
same form as the item ops. It is harmful when each item of the
sequence might be its own form (nested forms are problematic).

Default implementation of this method returns true. Specialize this
method to return false, if necessary. Note, this is done via a generic
function instead of a slot because it's an implementation specific
design choice. It cannot be changed at runtime and must not be visible
to the user of the widget.