box: use bitmap to check for missing fields in tuple_init_field_map

Reworked tuple_init_field_map to fill a local bitmap and
compare it with template required_fields bitmap containing
information about required fields. Each field is mapped to
bitmap with field:id - unique field identifier.
This approach to check the required fields will work even after
the introduction of JSON paths, when the field tree becomes
multilevel.

@locker: massive code refactoring, comments.

Needed for #1012