Fix repeated directives and Localized fields

[VjeraTurk]

#628

• LocalizedDescriptionSet renamed to LocalizedDescriptions
  Multilingual:
• Added in the SeatMapRequest a repeated language field
• In the response made LocalizedDescriptions a repeated field (to cater for all languages requested)*
• CountryEntryRequirementCategory, the Items made a repeated field
  Localized descriptions
• SeatAttribute, group name and destription into a new message and add the language so that we can insert it in SeatAttribute with a repeated -> made it like LocalizedDescriptionSet, where language is not part of the message but a part of set
• For section name used existing LocalizedString type

* should bot or "final system" filter the languages for the response?

[SamJaarsma]

LGTM

we keep CMP.types...LocalizedDescriptionSet message, because we think it is used elsewhere. Only the fieldname is changed localized_descriptions