Add missing `babel.cfg` files
Factor `entry_map`
Change `Field.value` to handle `Id_Entity` values

Add `_field_type_map`
Add `bool` to `JNJ.GTW`
Catch `Not_Found` in `resource_from_href`
Change `New` to add `_real_name`
Don't use `GTW.Form.Widget_Spec`

Add named templates `afs_input`; `mf3`, `mf3_input`, `mf3_v_seq`,
`mf3_h_cols`.
Implement GTW.MF3 and GTW.RST.TOP.MOM.MF3

MF3 implements forms for MOM (3 because it's the third try).

Still missing:

* Attr-Completers; except for attributes with a fixed
  number of choices.

* Display of errors; at the moment a browser alert is shown.