Use menu context for screen

issue3858
review5221002
Use the same read limit for children
Explicitly set value of parent field

issue3819
review5091002
Save tree state of menu when changing preferences

review5281002
Use Group.child_name instead of relation_field to skip on_change values

relation_field is not reliable see issue3899

issue3819
review6281002
Use a tuple model, dictionary for Reference field

issue3902
review9341003