Make all* Coma fields available for Metadata columns in EXAKT

[sarkipo]

Currently, only some part of Coma keys can be added in the Metadata dialogue.
E.g. under Communication, only Communication/Description keys are available (plus some hard-coded ones even if they don't exist in the coma file). But Description keys from elsewhere (e.g. Communication/Setting/Description, Communication/Language/Description, Communication/Location/Description) are not.
This is unlike Speaker, where all keys under any Description seem to be available (plus LanguageCode listed as Code in the dialogue).