Sort child screen as unsaved records

Child screen could contains records added using the add_remove of one2many and
so those records must be managed as unsaved.

issue3835
review5001002
get_preferences should not use the global context

issue3837
review5031002
Update sl_SI translation
Prevent D&D if the treeview is editing

issue3753
review4861002
domain inversion use None instead of False now

issue3844
review5081002