Fix files widget declaration

Files widget declaration is not done correctly, it should state:

<widget name="w_2_0" type="template">
<labels>
<label mode="any">files</label>
</labels>
<translated>false</translated>
<fields>
<field schema="files">files</field>
</fields>
<properties widgetMode="any">
<property name="template">/widgets/files_list_widget_template.xhtml</property>
</properties>
<subWidgets>
<widget name="item" type="file">
<fields>
<field>file</field>
<field>filename</field>
</fields>
</widget>
</subWidgets>
</widget>

instead of :

<widget name="w_2_0" type="template">
<labels>
<label mode="any">files</label>
</labels>
<translated>false</translated>
<fields>
<field schema="files">files</field>
<field schema="files">files/filename</field>
</fields>
<properties widgetMode="any">
<property name="template">/widgets/files_list_widget_template.xhtml</property>
</properties>
<subWidgets>
<widget name="item" type="file">
<fields>
<field/>
</fields>
</widget>
</subWidgets>
</widget>

Plus all options presented in this widget configuration is actually not configurable (these are configurations for the nxu:inputList tag, but all of them are not mapped in the list widget default template)