IndexMapping...
    types map[string]DocMapping
    defaultMapping DocMapping...
       FieldMappings []FieldMapping{FieldMapping{Name: "body_en", Analyzer: "en"}, FieldMapping{Name: "body_es", Analyzer: "es"}}


DocMapping...
    Properties map[string]DocMapping
    FieldMappings []FieldMapping (unpropertied field mappings)





some properties are "field mappings only"
  ==> graduate up to containing DocMapping as a "propertied field"

a named field would normally be
  DocMapping...
     Properties["description"] :=
       DocMapping...
         Properties := nil
         FieldMapping{ Name: "description_en" }
         FieldMapping{ Name: "description_es" }


example IndexMapping
  type [default]...
  type: beer...
  type: brewery...
    fields:
      name: description_en, property:
      name: description_en, property: "description
      name: description_es, property: "description
    nested mappings:
      address...
        named fields:
          city: city_en
          city: city_es
        nested mappings:
        field mappings:
    field mappings (uncommon, read-only)

