https://wiki.enredaos.net/index.php?title=CICICdev/august#GESTIO_DEV:_Un_widget_para_Foreignkey.28mptt.29
https://wiki.enredaos.net/index.php?title=CICICdev/august#GESTIO_DEV:_Un_widget_para_Foreignkey.28mptt.29
Done the widget, but need still some testing to see...
Unestable Foreignkey --> ManyToMany  widget