@GET
    public Map<String, String> getLanguages() {
        return languageResourceService.getLanguageNames();
    }
Returns a map of all available language keys to their corresponding
human-readable names.

@return
    A map of languages defined in the system, of language key to 
    display name.
guacamole/src/main/java/org/apache/guacamole/rest/language/LanguageRESTService.java